JC, it depends primarily on what CPU you are running, future upgrade plans and what you use your PC for.

The Rad8500LE (10% slower than Rad8500) is superior to the Rad9000PRO (20% faster than Rad9000). The Rads have 3D perf about equal to the GF3 cards, they lose out on AA but really benefit heavily from great image quality, dual display, TVout and DVD playback. A Rad8500LE or Rad8500 with 128MB can be found for under $100 and are great buys esp if your CPU is below an Athlon 1.4ghz as therer's less benefit to a GF4TI until your CPU exceeds this speed. Just check as clock speeds and functionality (dual display etc) often vary with manu and eom vs retail, worst hit is 10% perf and lack of dual display so check outt he price diffs, it may be worth it.

The GF4TI cards are enhanced GF3 cards sporting better 3D, AA, image quality, dual display, TVout/VIVO and they really get the most out of the faster CPUs. The best card to go for is the GF4TI4200-128MB which often o/c to 4400 speeds, very nice since they only cost $140-150. The 4200-64MB ($120-130) is also a good card and o/c's even better, but it isn't really a good idea to go for 64MB gfx RAM in any new card, there isn't a big diff in current games but there surely will be in the near future PLUS selling on any 64MB card is going to become very difficult. There are enhanced 4200-128MB cards which often reach 4600 speeds by using the more expensive 4400/4600 design and 3.3ns BGA RAM, eg Asus Deluxe, Suma Special Edition and Albatron P Turbo although these all tend to cost a fair bit more than the standard 4200 cards. For under $200 you can get GF4TI4400 which are about 10% faster than 4200, but 4600 only cost about $30 more and are again 10%ish faster than 4400. Manu makes VERY little diff for GF4TI cards so go by price, bundle and features.

For UT2003 the GF4TI4200 cards are tops, in fact for pretty much everything they are, fantastic all-rounders and my recommendation, esp if you have a mid to top range CPU or plan to get one in the near future.
PCstats - Albatron P Turbo
HardOCP - Asus Deluxe
Xbit Labs - Suma SE
Tech-Report - Rad9000PRO review (with other cards bms)
AnAndTech - Rad9000PRO review (with other cards bms)
GotApex - Average 4200-128MB review and what to expect from them