do you think for my comp it would make a difference if i got the ati radeon 9800 pro with 128mb instead of 256mb? the price is like half and there are more used available. the 256 is hard to come by and is over $200. i have the stock vid card in my comp and want to upgrade it. what would be most economical and best for my aging system?

Why are you upgrading it? Since you are on Macmod, you might consider a flashed PC card, or modding a card from a G5, there are limitations with both (ADC can be tricky if not impossible), but as with all these things, the more of the work you do yourself, the less you will end up paying.

There is a section on flashing GPUs to Mac on the forums at strangedogs, the best guys around hang out there to discuss flashing cards, and are happy to provide info and advice as long as you don't intend to profit from (just use it for yourself).

I did a guide on snipping off pins and overclocking an FX5200 from an early PMG5. The same tricks ought to work on most of the other AGP cards from those G5s, right up to the 6800s, but risking it on my £10 5200 is a far less daunting idea than trying it with a pricey 6800 Ultra. Worthwhile if it works though, doubt a better card will ever go into any G4. You can find my guide in the mods section here, or a similar one on XLR8yourmac.com.

uh...no hablez espanol? i can rock swapping out RAM and HDs but am a bit of a NOOB when it comes to serious mods. I'm open to anything but adding a new optical drive is a major mod for me. so, not all of that made sense but if you have some links to stuff I can check it out. where would i buy a flashed pc card? ebay?

They do show up on the 'bay yes.
Here is how you chop a G5 card to go in a G4:

http://www.macmod.com/content/view/603/193/

so all i'd need to do is get that thing for $50 and cut the pins so it fits into my slot and that's it? also, could someone answer my initial question too about the 128 vs the 256? And would this nVidia card be better than the radeon card?

the 9800 pro with 128 MB will be just fine in an MDD. remember this card has an extra power connector for the highter power needs!
if you use a G5 card (i think that would be the XT with 256 MB) by chopping off the "surplus pins", the card will draw all its power from your poor logic board.
(i am not talking about the ADC-connector, which would be easy to get working)
it wouldn't be the first MDD dying because the AGP card draws much more power than the lobo was designed for to handle.

just remember the additional power connector on the 4x AGP 9800! it does have a meaning.

but hey, this is macmod. no risk no fun. am i wrong?

but what i wanted to say: the FX5200 is a slow card compared to the Radeon 9800. plus there is the power draw problem. might work, but could damage your MDD.

i had a 9800 4X AGP with 128 and a 8x AGP 9800XT with 256 in my G5. didnt really see much difference in performance when playing UT 2004.

maybe there are other applications that benefit from doubling Vram, but i wouldnt spend much money for it. just my humble opinion. not very scientific either

VRAM might make more difference if you run two displays off the one card.

so maybe i'll just get the ATI radeon 9800 pro 128mb instead of the 256mb and wasting a day screwing around with the $50 nVidia card. I can find the 9800 pro 128mb used on ebay. Is that additional power connector going to be a problem? Will I need additional adapters? Should I purchase an extra PCI Fan to cool this beast down some more? How much can I resell the ATI Radeon 9000 Pro for?

good choice. you will certainly feel quite an acceleration with the new card.
also the 9800 was specified for the use in this mac and will not draw more power than your MDDs AGP-bus can handle.

the extra power plug for the radeon 9800 / 128 is no problem at all. it uses the same plug as every diskdrive. the retail box even has a Y-adapter included.
the stock cooler on the 9800 can be noisy. there is not so much choice to use other coolers such as an arctic cooling solution, as one or two ram slots will be blocked by any taller cooler (have a look at my unreal mark2 mod, where this problem can be seen too)
a pci slotcooler might help.
or just leave the pci bezels away first for some improved air flow.
dont now about resale price for the radeon 9000 at your place. in switzerland it is about 80 francs (maybe 60 $)

@waragainstsleep: right you are. i forgot about the dual monitor thing. the vram will be split between both monitors. but in most games the second screen will be shut off anyway.