I have an older machine, it's a P4 1.6. It currently has an AGP 4x video card with 64 mg memory that I'd like to upgrade for gaming. The AGP slot is 4x. Would it be better to replace the current card with an 8x card that has more memory and let it run at 4x? Or.... would it be better to yank the AGP card and install a better PCI card with more memory?
You should be able to right click on your desktop and under settings it well say xxxxxxx monitor on Geforce XXXXX. If it is a GF4Ti series card, you can't improve it much for $125. It may be a GF2ti 64MB DDR, or even a GF2MX400 64MB, or GF2 GTS 64MB, GF4MX, etc. Any of those those DX 7 cards would be definately worth replacing within your budget, as would GF3 or GF3Ti200 DX8 cards.
Are you in the USA? If so, For $125, best chocie would be a radeon 9600XT or save money on a Radeon 9600 pro for just over $100. For $113, this new <A HREF="http://www.gameve.com/gve/store/productdetails.aspx?sku..." target="_new">Radeon 9500 pro</A> would be a nice performer and is faster than the 9600pro and pretty equal to the 9600XT. (shoot, it says backorder now, was in stock last night) The best you can do for around that price is a used/refurbished Radeon 9700 pro.
Now you may be wondering why all these are ATI cards. Simply because they offer the best bang for your price range. You need to spend about $200 before the clear best choice is a NV GF6600GT. The GF FX series doesn't compete with the Radeons for the same price, so avoid them. Another cheap option for you would be to buy a cheap used GF4 Ti4200, 4400, 4600 card. Only DX 8 cards, but still a good bang for the buck.
From best performer to worst, and most expensive to cheaperst, I would say choose from theses cards:
Used Radeon 9700 pro
New Radeon 9600XT or 9500 Pro
New Radeon 9600 Pro
Used GF4 Ti4x00
Edit: Cheap new Radeon 8500le
I've heard of the MX200 and MX400 as well as the original GF2MX which was between the two in performance. But I have never hear of a MX100. Anyway, yes, you could definately use an upgrade. On a budget, a Radeon 8500le would be a huge increase and they can be found for $35 new sometimes. But the other list would all be above the 8500le even. So it depends on what you want to spend and what games you hope to play.
I am basiclly in the same boat as you. I have a 256MB AGP Nvedia card and want to upgrade to a faster card with more memory. Some have suggested that a faster PCI card with more memory could be an improvement and others say no. I do video editing and redering is always sent to the video processor so speed is essential.