Dual Socket Server Build Under $2k

Hi,

I am looking for the best dual socket server build for around $2-2.5k.

Something like a Dell PowerEdge T710, which I was able to spec out the following for about $3.6k

2x Intel® Xeon® E5645 2.40GHz, 12M Cache, 5.86 GT/s QPI, 6C
32GB Memory (8x4GB), 1333MHz Dual Ranked LV RDIMMs for 2 Processors
No OS

Requirements:
- dual socket, HT or QPI (which is better for computation?): AMD or Intel ok (just want best bang for the buck)
- room for memory expansion (the T710 can go up to 144GB = 18x8GB)
- can handle standard Hypervisors (with Ubuntu and Windows 7 on top)
- 1100 Watt Redundant Power Supply

Applications:
- computational server (95% of the time)
- low-midrange gaming (5% of the time)
- my application is custom written in C++ so I can use as many threads as feasible
- Mysql

Preferences:
- any suggestions for HDD so I can avoid bottlenecks would be greatly appreciated
- server will always be on, so lower power usage during idle would be nice
- prefer to focus spending on CPU and memory, decent MoBo
- hope the server can last 3-4 years until replacement

The machine I am replacing is an HP ML115 AMD box I bought 2.5years ago for about $600 (dual-core 8GB RAM), so I'm wary about spending $3k+ on hardware (especially with the current rate of hardware improvements).

TIA for any suggestions.