I've been a computer (ab)user since 1983.
Aside from my first few, a TI-99/4A, a Xerox 820-II, a PCjr, a model 5150 IBM PC, I've assembled all mine from various parts and pieces. (There's also the various Macintoshi I've had, but until they went Intel they were Macs, not PCs, aright? Some of those I had to put together from bits too.)
DDR3 in a triple channel configuration is currently the newest and fastest RAM. If you're a *serious* gamer, a sub $100 PCI Express x16 video card is just not going to get the job done. Wikipedia has very good articles on the specifications of all the ATi and nVidia GPU chips.
As for the power supply, more watts = better. Make sure to get one with the right plugs for the motherboard, video card, additional CPU power and all your drives.
Peruse this page for power plug info.
http://www.playtool.com/pages/psucon...onnectors.html
As for the drives, get SATA. It's faster than the old IDE and the tiny cables are easier to keep out of the way of other things.
If you *must* have a floppy drive, there are still a few boards made with the connector, usually also including one IDE connector.
If you want to connect it to a TV, get a video card with an HDMI connector. It will have an SPDIF connector to route digital audio out through the HDMI.
Unless you're a super "golden ear" audiophile type, the built in multi-channel sound on most motherboards is perfectly fine. Don't waste money on a super fancy sound card, unless you really really want to.
The way to get a PC booting faster is with a Solid State Drive or SSD. Install the operating system and programs to it, but save all your data to a hard drive. look up how to redirect your web browser caches to a location other than their defaults.
An SSD can wear out, but current ones are very robust. NEVER use a defragmenter on an SSD. It's completely pointless. All solid state storage devices (except the very earliest ones from the early 90's nobody uses anymore) use a "wear leveling" system where writes are randomly scattered across the chips. "Defrag" it and the files will appear to the OS as if they're not fragmented, but will still be scattered randomly.
There's no track to track or sector to sector seek times with an SSD. Every memory cell is accessible at the same speed. Defragmenting an SSD just puts more wear on it.
I'm still using the same 12 bay giant tower case I bought in 2000. I dubbed it "Megatower 2000". I was fed up with weeny little mini and mid tower cases all cramped and hard to get into. It's been through a succession of motherboard, drives and other pieces to the point where only the case remains from the original Pentium III system. Its last major upgrade was to an AMD Athlon 64 3500+, Socket 939 - circa 2005~06. I just got another gig of RAM (DDR1) and ordered a 64x2 3800+ CPU. Other cheap PCs with supposedly faster CPU and RAM tech have come and gone, ye olde big box beat them all.
'Course if I put together something with a 4 or more core CPU, triple channel DDR3 and all the really latest goodies, Megatower 2000 would be left in the dust.
One thing I really want to upgrade is the RAID 5 array. It's four 200 gig SATA II drives connected to a PCI *hardware* RAID controller with all 4 ports internal. Such a card was insanely hard to find. Most of them for some reason have 2 internal and 2 external ports and/or use software driven RAID.
The thing with a hardware RAID controller on a plug in card is it's completely transparent to the OS, appearing as a single drive, and the card and drives can be moved to another computer without having to backup the data and rebuild the array as must be done with a motherboard integrated RAID controller. (Unless the new board uses a 100% identical controller and RAID firmware.)
I'd love to get four 1TB drives for it, if I can find a super deal. I got the controller on eBay at a low price and the drives are OEM "white label" Seagate, around $200 for all a few years ago. Total storage with the RAID and other drives is 3/4 TB.
I've a single 1TB external drive connected to another PC - I *need* to upgrade MT2K's storage situation.
As for a case, how about something like this?
http://cheezburger.com/6875364096