Yup, with a Cely 950 you won't be getting anything out of the 4200 you couldn't get out of a GF3 or Rad8500, but you should find a 128MB GF3 or Rad8500 performs better, esp over the coming months than a 4200-64MB, if you had an AthlonXP1800+ or P4 2.0ghz (or better) then the 4200 even with 64MB would be the better buy. Well to say the 4200 with a Cely 950 would give 'nothing' extra isn't entirely true. It should be a smidge faster than both and will certainly give a lot more when the time comes to upgrade your CPU. In addition over the GF3 it has much better image quality, dual display, TVout, Quin AA and will sell on much better. Over the Rad8500 the 4200 sports HUGELY better AA (esp in 2xAA and QxAA) as well as better quality (but slower) Aniso. So if you want AA that pretty much rules out the Radeon cards (excl the wonderful Rad9700) and if you want much better image quality, dual display, TVout and the ability to eek out lots more perf with a faster CPU then 4200 is certainly the way to go. That's my take on it anyway!
NV30 isn't going to be selling sub-$150, certainly for a good while and there's been no news of the Rad9500 either. I'd suggest a 4200 for the above reasons but if you aren't going to be upgrading your CPU in the coming months then you'd be better served really getting a Rad8500/9000PRO or GF3 esp in 128MB versions. NV28 is scheduled for release any day now, but how long you want to wait for availability, prices to settle, reviews to come out etc etc really does mean you could always be waiting for the next big thing. I'd say you really need to consider a CPU and therefore mobo if not RAM too. With AthlonXP1900+ type CPUs being so cheap it really makes sense to put your money there, there are a few SktA mobos which possess both SDR (PC133) and DDR slots which can take the sting out of the upgrade. Current Pricewatch prices show AthlonXP1900+ $80 or XP1800+ $69 (same price as a Cely 1.3ghz) and SktA mobo are only about $50 too. Using SDR PC133 would only knock perf about 10% which isn't too bad considering the huge leap in perf, at least then you'd be able to get a whole lot more out of any gfx card you choose.