According to their website Vegas supports OpenCL which is supported by nVidia and AMD alike.
No case?
Check out Gumtree or the OCAU classifieds for a decent 2nd hand system. $600 AUD on a new system wont buy much at all. You should be able to get an older i5/i7 + gtx680 era gpu for that money.
The GTX 760 is still better in games but the AMD will probably be better in OpenCl sooo? Plus when you record the Nvidia has that Gameworks thing that lets you record with a negotiable performance hit but IDK Hard decisions.
I would try my luck with a GTX 760 personally But Ive had problems on my 280x (Probably because i made my Driver because the AMD ones did not work for my GPU.......) that said not everyone gets the same problems.
That being said the R9 270 is still one beast of a card and i think the MSI ones come with a free recording software that does not effect performance that much.
How does this look? https://www.pccasegear.com/index.php?main_page=wish_lists&wlcId=463654&action=wish_lists
Are these Australian prices? Some of the prices seem off, especially that CPU. The 6300 is just $90 US for me, for example. RAM seems kinda high too, even for 16GBs. No certificate on the PSU?
Other than that, it looks good. You can't squeeze premium performance out of $800, but this should get you by for a while. Try to get a 6300 at least instead of the 4300 bc of core count.
Yeah Aussie prices I live in Australia