Not bad, but cases are a dime a dozen.... however you should most definitely decide what type of system you want to build, because not all motherboards fit in all style cases. A regular sized ATX board will not fit in say a MicroATX case, etc.
You need an idea of what you want to build first, because if say you want to build a server, or something with a lot of drives, you need room and huge airflow, and places to put fans...so you would need a full sized tower...those are big, by the way. The average tower-styles for most stand-up pc's you see are mid towers. Those are nice, average airflow, and fair room to work and wire.
You should decide case and motherboard to be compatible, however you choose. Airflow is a big consideration especially for gaming. Gaming systems run hot, and need space and cooling even moreso than everyday systems. If building a gaming system, go for a full sized tower!
But, honestly, unless you want fancy, the most important thing is to design around your components. Do you want something that you can upgrade? Is it a gaming system? How much room do you need? How many bays? What is airflow like? Does the case come with fans? How many and where on the case are they located?
Look at the motherboard...where is the CPU,North Bridge, and Ram located? Are they straight across, making a heat trap over the CPU, or are they angled and better positioned for airflow like some newer boards are (BTX motherboards, though for some reason discontinued, actually had a better design allowing for better cooling of the CPU. Google images of both, and you will see exactly what I mean!)
Motherboards... you want something that will not be obsolete tomorrow! You want to be able to upgrade! therefore, if trying to save money, you might want something that takes a dual or quad core, but is upgradeable to quad core or higher, and just start off with a dual core. Also, you need to make sure the CPU comes with cooling, otherwise you need to buy a heatsink,fan,and thermal compound for the CPU.
Memory- you want as much RAM as possible in upgrades...remember though that you need to watch the speed as well as the size. The first set of numbers, the ones without the MB's, tell you the speed, like a 133,266,etc. and you need to make sure the memory is all the same speed.
You need to know the number and speed of the buses on the motherboard as well. Buses are basically the pathways the information takes.
If you are going to do graphics work, multimedia, rendering, and/or gaming, you will need a good graphics card. Some people like ATI Radeon, some like GeForce NVidia. I have used and like both, HOWEVER, be careful to get your updates FROM THE SITE, NOT through Windows update!!!!! There was a BAD error in the last Windows 7 update that installed the wrong driver for NVidia cards and screwed them up royally! They worked fine for a few days, then the screen went black completely!!!
Also, be careful of the particular manufacturers. Many different companies make these cards,not just one, but use the same name. PNY mkes some NVidia cards, however several people have had trouble with the fans on the cards dropping, falling, and shorting out the cards, or just plain not working and burning them out! If you buy a PNY card with a fan, you "may" need to replace the fan, so keep your eyes open!
Hard disk- Solid State is "best"...but extremely expensive! Here's what most people I know do- they have 2 hard drives, a nice small one for the main operating system and some "important" programs, and then a larger one for storage and/or other programs. This is because if anything goes wrong, it's easier to wipe out and reinstall an operating system on a smaller drive that only has an operating system on it, without losing a lot of time or data.
And honestly? if you download a lot, get yourself a couple external drives for backup and storage. That way, those files can be scanned for viruses before being moved, and you always have a clean drive to store things such as your anime downloads and music :)
Now...don't forget a MONITOR! These days you can get a decent widescreen LCD fairly cheap...but if you have the cash, and/or a real nice Digital TV...just hook it to that! :D
And if all this panics you, the best starting point in the world, is a BAREBONES KIT!!!! Worse comes to worst, you can build it, and sell it to someone for more than you payed, and build another...because you will want to after you build your first monster...it gets in the blood, lol! :D
EDIT: want to explain what I meant by cases being a dime a dozen. Unless you are looking for something fancy, or unless you have limited space, not only can you get a cheap tan case with most of what you need, sometimes you can get a decent case along the curb on trash day, because for some reason people throw out an entire system when they upgrade. Cases literally ARE a dime a dozen. Some come with power supplies, some don't. New ones are nice, everything snaps in place, older ones take a bit more work, but cases are easy to find either way. Don't build your systrem around a case, because you may accidentally limit yourself. That cool looking cube has terrible airflow, not a lot of work room, and not a lot of room for expansion! Cube cases by the way are usually in 2 sections! They only APPEAR big on the OUTSIDE! they are split in half on the INSIDE!
Always figure out both what size you want AND what motherboard, and design the system together as much as possible! Anyone can pick out a really killer case...but if the motherboard won't fit it, what will you do then??? If the cooling sucks and you fry your system, what next? Design the case around your needs, both in space and expansion, and make sure your case and motherboard fit! When you buy a case, if you HAVE a power supply, don't buy a case that comes with one, because that extra money you are spending is wasted! If you do NOT have a power supply, buy a case that not only has one, but one that suits your power needs. Don't waste money on a 350 watt power supply /case combo and then buy a 500 watt supply. Either buy the two separately or make sure the case comes with a 500 watt supply!
