Upgrading questions

Hi, I bought a 27" Imac a couple years ago and had recently upgraded the RAM to it's max at 16gb. Now I'm curious at what else I can do to get this bad boy running even better. I'll post my specs below.

Model Name: iMac
Model Identifier: iMac11,3
Processor Name: Intel Core i5
Processor Speed: 2.8 GHz
Number Of Processors: 1
Total Number Of Cores: 4
L2 Cache (per core): 256 KB
L3 Cache: 8 MB
Memory: 16 GB 1333 MHz DDR3

ATI Radeon HD 5750

P.S. I'm not very comfortable with upgrading any "MAIN" stuff like CPU's and whatnot. Just thought I'd throw that in there. Any help would be much appreciated. Thanks

 

Awesome. Thank you guys for the reply