Kimps, have you checked the MacBook Pro? It has a full 128-256MB of video RAM and yes, it is discrete and not integrated. The MacBook, otoh, uses the Intel GMA GPUs with integrated memory. This is the reason why I opted for the MacBook Pro instead of the MacBook.
If I were you, I’d get a MacBook Pro (assuming that the MacBook will never get a real video card) and an 24″ iMac or a MacPro with 30″ Cinema display, if you can still afford it. Use the hardware to dual-boot Mac OS X and Vista (for games!). :P