Hi...I'd agree with the others, that if you can make some time to do a little research on building a pc yourself, that would be the best in the long run. The flexibility is endless- do you want a quiet pc, a power house, cheap, etc- you can tailor it to your requirements. I built a recent AMD 3.3Ghz quad core, 8GB of memory, ATI 5770 video card, SSD hard drive, for around $1100 for a htpc. I went overboard there a bit, but I do use it for gaming too.
I also built another pc with left over parts (dvd drive, hard drives case for a few months) for my office for about $600, another AMD quad with 8GB of memory. This pc is not done yet, later this year I'll replace the hard drives and add an external video card. But in the mean time it's serving it's purpose (I'm going to install Lord of the Rings Online tonight to see how the onboard video works). So you also have the ability to build over time, get something workable now, and add/upgrade later down the road. This ability also pays dividends as the pc ages and you want to upgrade. Sell the old video card online, get a new one, etc. You may not have that ability or be more limited with a name brand pc.
If you don't have the time for research, there's enough people here that have the knowledge they would probably be willing to make recommendations on components. Then if you like the specs and price and feel up to it, place the order and assemble. Most things only connect one way, and the motherboards instructions will cover most of it. Good luck with whichever way you decide to go.