Radeon 7870 on Antec VP450

Hello, I've searched and came up with a similar post but there was no follow up to it, so I'll ask here.

I have an Antec VP450 http://www.newegg.com/Product/Product.aspx?Item=N82E168... that I purchased because it was on sale and got some really good reviews. At the time I wasn't aware of it only having 1 pci-e power connector, and was satisfied with my current graphic card (a trash 6570) since I only play smite and GW2. It's been enough, but recently I've felt like turning up some settings, and also have seen the price of the 78xx series drastically dropping in price.

The 7850 has hit 190-200 a few times, and just recently I've seen the 7870 (although it was a sapphire that had many black screen problems) but this morning I seen this:
http://www.amazon.com/gp/product/B007KJ1UTY/ref=ox_ya_o...

It was 201 this morning, and now its 196, and seems like too good of a deal to pass up.

So I had 2 questions; because my PSU only has 1 pci-e connector will the use of an adapter be safe? I seen some other threads online mention that you should never use an adapter because the PSU wont have enough power.

Also, how is VisionTek as a company? I've only ever bought sapphire, and with the recent black screen problem I'm looking to try a different brand.