How far will the ASUS/Nvidia 6150 chipset take me?

Hi, I just bought a ASUS M2NPV-VM motherboard with an nVIDIA® GeForce 6150 + nForce 430 chipset. I built this PC to use as a Home Theater PC but would like to be able to play games. I realize this is not a good as a high end card, but what does it compare to? At what level will I notice the performance will take me no further? Also, I am a little confused about the Ram size. On a dedicated graphics cards clearly 256mb or 512mb is easy to understand. How do I measure or compare minimum requirements RAM to those when buying a game? The ASUS bios has entries for 32mb,64mb,96mb,128mb, or disabled. (I have it set to 128) Not sure if this is directly the same as the RAM size, or if it even affects it. Within Windows XP MCE the adapter properties show 512mb RAMDAC. Is this the number I use?

Also, another strange thing is that I cannot play my DVD because of MAcrovision. I have the latest video drivers. I even bought nVidia's purevideo encoder thinking it would fix the problem. I can rip the DVD;s to disk and they play fine. Any help is appreciated