Excess memory will slow your machine, the memory controller has more memory blocks to account for, meaning that data stored on the RAM takes longer to retrieve. In addition, the RAM will get fragments all over the place, not to mentioned added latency.
Memory size needs the proper speed to compensate, same deal with VRAM, no point to buying a 6200 with 512MB if it can't utilize the memory properly.
BTW, I'd take an LCD projector over the grand canyon, possibly one of those three colour projectors (can't remember what they're called).
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w