There are too many reasons even more so when we talk about video work.
Ok, the warranty is split into a few areas. Yes you'll not get any warranty support for the OS. It was not that good anyway as most questions end with "restore the factory OS."
But the hardware is still under warranty with something you must know going in. They won't support you with a hardware issue unless you restore the factory load. Some get upset about that but 'dems the rules'.
While the x4500 might be slammed by some, outside of games I find it a great solution. My laptop with a 4500MHD connects to the HDTV with HDMI and plays HD content just fine. And with your i3 you'll scream past my laptop's older C2D 2.0GHz CPU.
I built our computer about five years ago so we are well past the time when it needs to be replaced. I've been upgrading RAM and storage as we go, but we've reached the end of the road with this one.
I'm considering two different computers for purchase: one is a refurbished from buy.com, and one is a newer tower from Best Buy. Regardless of which one I get I plan on installing a second hard drive (to separate the operating system from the data) which I'm guessing would void any warranty that comes with the machine. So bear that in mind. (related thread: http://forums.cnet.com/5208-4_102-0.html?threadID=388908%20)
I don't do any gaming or video editing so we are looking at photos, music, streaming video, etc.
Gateway DX4822-01 (refurb) $399
2.6GHz Intel Pentium Dual-Core E5300 Processor (Benchmark = 1723 on cpubenchmark.net)
6GB DDR2 Memory
1TB 5400RPM SATA Hard Drive, 16X DVD