I was thinking about buying a new computer, preferably a Mac. I'm dual boxing right now using Synergy with an older pc + macbook air combo, but I'm getting a really bad framerate on both computers, even with low settings. Thanks in advance for reading!

Specs:
iMac: $1,199.00
21.5-inch: 3.06GHz
3.06GHz Intel Core 2 Duo
4GB memory
500GB hard drive
8x double-layer SuperDrive
NVIDIA GeForce 9400M

Mac Mini: $750.00 + Dual PC monitors (suggestions where to buy?)
2.26GHz : 160GB
2.26GHz Intel Core 2 Duo
4 GB memory
8x double-layer SuperDrive
NVIDIA GeForce 9400M