Help Deciding Which New Mac Mini to Buy

I plan to replace an old Dell desktop running Windows XP SP2 to one of the new 2011 Macs running OS X Lion, most likely a Mac Mini. I have a few programs that I want to run on XP SP2 within Parallels for Mac 6 including Quicken, Adobe Acrobat Professional, etc. but no games or anything graphically intensive. If I plan to keep the Mac Mini for 3-4 years, which processor and HD combo should I buy to ensure good Parallels for Mac 6 performance and OS X Lion performance?

Processor
2.3GHz dual-core Intel Core i5 with 3MB on-chip shared L3 cache or
2.5GHz dual-core Intel Core i5 with 3MB on-chip shared L3 cache or
2.7GHz dual-core Intel Core i7

Hard Disk
5400 RPM or
7200 RPM

Thanks,

 

Either way, I'm planning to configure with 8 GB memory.