|I assume that you are talking about building a new system since you already have a quad and the CPU you mentioned is not compatible with your motherboard. |
List your budget for us to get a better idea of what you can afford.
If you are not looking to build yourself, you will need to either customize the build (like is available on HP's site and similar), get it build for you, or get the closes match you can and upgrade the rest. The best option would be to build it or get it build for your needs.
Ideally, you want a 4th gen. i5 or i7 quad, a quality compatible (Z87) motherboard, a serious graphics card (around a GTX660 w/2GB GDDR5 or higher (GTX650 Ti Boost might do)), 16GB (2X8GB) (or more) DDR3 1600 Dual Channel matched set RAM, a high quality power supply, and a good roomy case. I did say ideally so budget would determine the details. Do not skimp on the CPU and motherboard too much if you can since they are the more difficult to upgrade later (upgrading or adding more memory or even upgrading the graphics) is much easier. This is real important, absolutely get a high quality power supply that will be able to power the most you might wish to go with. This does not mean very high wattage, but enough wattage and the best brand and other specs.
Give us your thoughts, possibilities, and budget and we will comment on specifics and give more suggestions.
You have to be a little bit crazy to keep you from going insane.