I have a dell zino hd with a 3250e 1.5ghz dual core am2 teamed up with a hd4330 512 meg notebook mmx video card.I have no ploblems playing a blu ray let alone a MKV.....The 6450 with 160Sps has twice the shaders over my hd4330s 80Sps,along with twice the video memory 1gig over 512mb.
I also noticed my ati card has nicer colors then my 560tis,are you streaming your content or is it coming directly from you HD in your machine the 6450 is in....The only time my 4330notebook card really flops os if its not getting a good stream of information...I am on a lame wireless g network with that zino and very choppy high bitrate stream can be corrected by downloading the file onto the zino machine before i watch it.Mabey you are having the same network speed problem i sometimes have??
Anyway i feel the ati/amd cards give a better more vibrant picture then Nvidia cards in my opinion.
Looking on newegg i see the galaxy gt430 goes for about 54.99,found a sapphire 5670 with 400Sps and gddr5 memory for 54.99refurbished....but i think your best choice if it will fit in your rig is this HIS dual slot 6570 with 480 Sps for 64.99 then add a 10$ rebate would be the quietest card of the bunch http://www.newegg.com/Product/Product.a ... llFullInfo
.... or for another 5$ you can get a sapphire 6670 that has 480SPs and hotter clocks then the his card and it had a large fan so i do not think noise will be a problem http://www.newegg.com/Product/Product.a ... 6814102952
the 5670,6570 and 6670 all are much more powerful then the gt430 from the green team. The 5670,6570 and 6670 will even allow for some half decent gaming, all for a tiny premium over the gt430.I will say it one more time from my point of view the ati cards have a better picture then then the gt430 for home theater purposes.Whoops i forgot to add all the cards i listed do not require a power cable,they get all there juice from the PcI-e bus:)Also make sure you are using a playback program that supports HW accel,something like Media player classic Home Cinema aka MPHC,Even VLC....i use both since VLC is great for playing ISO images.But MPHC lets you use the programs shader combinations Edge sharpen works great along with de noise for lower quality stuff.MPHC has a lot of key shortcuts like CTRL/ALT/P to enable post screen space shaders or disable them,it comes in a 64 bit version or 32 bit.
Hope this info helps you make your mind up. Peace
UPDATE now that i looked at the HP miniserver rig i am pretty sure you can find half height cards in the same models i posted if not do what ya have to do.But i do thin your ddr3 1.3ghz turion has more power then my ddr2 1.5ghz 3250e X2 but not positive on that.Here is a halt height passive cooler 6570 from his same price as the dual slot model http://www.newegg.com/Product/Product.a ... 6814161390
..here is sapphire Half Height 6570 with active cooler http://www.newegg.com/Product/Product.a ... 6814102942
..here is a HIS 6670 half height card with GDDR5 memory but its a little over 90$ http://www.newegg.com/Product/Product.a ... 6814161397
..if you want to do some light gaming the LAST CARD I POSTED will do the trick a pretty powerful half height card...read the customer reviews and go from there....but i do not think you will find a better half height card.That does not need a Power connector to the card but if you PSU can handle it they do make a half height 6750 with 720 SPs for 140$ http://www.newegg.com/Product/Product.a ... 6814131448
..you might have enough power to run this since this fella is with.."QUOTE"The Radeon HD 6750 has a Thermal Design Point (TDP) of 86W. In other words, that's the maximum amount of power it's designed to draw out of the box. The 450W recommendation is simply a safeguard; I'm running it just fine on a 275w PSU, whilst powering a USB3 pci-e adapter, a core i3-560, an optical drive, and three HDDs. It runs fine, but watch your 12v rail (11.26v under load here).
Biostar Eco i2 barebone with 275w PSU
Core i3-560 OC'd to 4ghz
G.SKILL Sniper DDR3-1866 2x4GB
I noticed you have a 150 watt PSU if i am looking at the correct HP rig.....you dual core turion only uses 12 watts loaded with the lower power ddr3 memory you will be rolling the dice with the last card i posted that needs a power connector,I would stick to the 6570 it will still allow some light gaming and may even play some later game at low setting and at 1080p....I know for a fact you would get great frame rates with a game like LFD2 at 1080p
Another update i just watched a video review on the 1.3ghz hp server and it peaked at 41 watts loaded with 4 HDs so i am pretty positive it will handle the 6570 or 6670 card with the little 150 watt PSU perhaps even the 6750.....i also looked at the motherboard installed in the thing and noticed right next to the PCI-e 16 slot it said 25 watts hopefully thats not all the watts that slot will supply to your video card,I do not know of any way to test that to see if thats the case with the slot hopefully its for the PCIe 1x slot:)
Good Luck. The official TDP of the HD 6670 is 66W so the 6570 will be a bit lower.Hope all this info helps...I think the gt430 pulls 49 watts.Just dont run furmark:)