What does 3dMark actually mean in terms of games?

I'd suggest you revise your plans a bit ...

You can't do it for $90 ... but you can stay under $200 and upgrade to a MUCH better system by using this motherboard:  http://www.newegg.com/Product/Product.aspx?Item=N82E16813157107

... and getting the bottom-of-the-line Core 2 Duo:  http://www.newegg.com/Product/Product.aspx?Item=N82E16819115013

This system will be MUCH faster than what you've suggested above;   will let you use your current graphics card and memory; and will support an upgrade to a PCI-e video card (and DDR2 memory as well).    ... and with your current video card, your 3DMark scores will be better than you get now, because the CPU is SO much faster than what you currently have.

... the motherboard also supports MUCH faster Core 2 Duo's --> including Quad Core CPU's --> so if you ever want to upgrade again all you have to do is buy a better CPU :-)

The best computers for games donot rely soley on a great video card but the balance between   good supply of ram
good  PSU
 fast processor with good ventilation.
3DMark is a computer benchmark by Futuremark (formerly MadOnion) to determine the DirectX performance of graphics cards.
The measurement unit 3DMark is intended to give a normalized mean for comparing different visual processing units, which proponents assert is indicative of end-user performance capabilities. Critics counter by stating that it is not a reliable measure of real-world performance.
There are seven different versions of 3DMark:
3DMark99
3DMark2000
3dMark2001
3DMark2001 SE
3DMark03
3DMark05
3DMark06
Real performance in games is not determined by this benchmark. Because of this, 3DMark's results have increasingly come into question over the years; while 3DMark01's results largely tallied with overall game performance (a result of it being built on the Max Payne renderer), 3DMark 2003 proved almost totally divorced from realistic gaming scenarios. One hardware site performed tests on the benchmark, and found that in 3DMark 2003, a system using a Pentium II and a Radeon 9800 would perform only slightly slower than a system with the same graphics card and a top-of-the-line (at the time) Pentium 4. In real-world games though, the Pentium II system would be totally unsuitable for playing (then-)modern games on. This caused 3DMark 2003 to lose most of its credibility
http://en.wikipedia.org/wiki/3DMark#3DMark06_features

My personal choice for the best gaming card is nvidia as  of course I own one.
XFX GeForce 8800 GTX Video Card
http://www.motherboards.org/reviews/hardware/1671_23.html