Don't knock on Dell so much; I'm running one of their 400SCs and it's one of the finest, most stable computers I've ever used.
Can you tell us more details about what CPU-Z says concerning RAM speed and timings? The RAM is likely to be CAS3 high latency RAM that will not overclock well; and it might not be PC3200, which is really what you need at minimum for your new rig. If you're building a Winchester rig, you'll probably want to overclock.
If you're on a budget, I'd suggest some inexpensive Corsair Value Select PC3200 CAS2.5 memory; about $160 for 1GB (512MBx2); if you overclock with this RAM, you will have to use your motherboard's RAM dividers to keep the memory frequency around 200MHz. If you plan on overclocking and want RAM that will run at high FSBs, look at PDP XBL memory at Newegg. It's around $230 for 1GB (512MBx2), but it is often good to memory clock speeds of 270MHz+ at low latencies.