HD files on tv screen, not sure what to do, advice needed

[stammie]

A little background before I get to the nub of my dilemna,
at present I use an xbox with xbox media centre to watch all my media upscaled on my tv,
I almost adore this combination, I regard xbox media centre as the best software I have ever used, far superior to any commercial program I've used on any platform, but..........................
I now want to also play HD files on my tv.
I'm considering either a networkable dvd player, (the Helios X3000 seems to be the unit I'd choose) or upgrading my pc.
The Helios's only advantage over xbmc is playing HD files, everything else I've read about it seems to be a backward step.
My pc is hopelessly out of date, everything except the graphics card is getting on for 4 years old, even the graphics card is old(a geforce 5700fx),

my question is, if I just updated my motherboard, ram and processor (I've seen 1gb of ram, AMD 3800 Athlon and nforce 4 mobo for less than the helios box) and got a dvi to hdmi lead to connect to the tv would I be able to play HD files ok?
I haven't considered updating my pc for so long as it does everything I want it to and even the technophile in me couldn't justify spending money on it,
I'm not interested in a full HTPC, just the ability to play HD files on my tv from the hdd on my pc.

As the title of this thread says, advice needed, any will be greatly appreciated

[dan1979]

What are your PC specs exactly?

My AMD2800 Barton/Geforce Ti4200 played the majority of HD stuff just fine. Only WMV-HD 1080p and H.264 1080i stuff tripped it up.

What sort of HD files are you playing?

There are no stand-alone players that can manage h264 content yet and you need a beefy pc to do it (dual core). If all you've got is MPEG-2 stuff then it's not too much of a problem with a slight pc upgrade or something like the showcenter for little over £100.

[stammie]

my pc has a 1.8 ghz AMD Athlon,
I'll be playing HD divx, xvid and mpeg files,
I don't think I'll want h264 playback for a while so that wont be an issue