Slow GPU Rendering Issues With Sony Vegas Pro 11

Hey all,

I'm new to the forum but have been here before looking for answers to other various questions and have found it to be quite useful so I'm hoping I can get more useful information for this recent issue.

I do a lot of rendering as I have a few Youtube channels and as such I was hoping to reduce rendering times via GPU acceleration. Previous to today when I installed my new SLI GTX 560ti Core 448 1280mb cards I had SLI GTX 460 1gb cards. I was kind of pumped to try out rendering with the new cards in (I know it only uses one) but much to my surprise I had the same issue I had with the 460: my CPU renders video faster.

I render in both 720p and 1080p MP4 from FRAPS files. With SC2 videos there are two overlays (static media in the form of PNGs) on the videos. Rendering time with my CPU is a little less than 3x the length of the video in 1080p (10 minute video = about 27 minutes of rendering time) and with my GPU (both the 460 and 560 448 core) it's either about the same or a bit slower. GPU acceleration is turned on, the card is selected, and the profile I'm using to render is set to use GPU when available. I have also tried leaving it on automatic. 720p video is about equal as well but is obviously much faster than 1080p.

The files being loaded into Vegas are coming off of a WD Caviar Black 1tb 64mb cache SATA3 drive (the drive is plugged into a SATA3 port with the appropriate cable) and renders usually to desktop which is another WD Caviar black 1tb 64mb cache SATA2 drive cached by a 40gb Intel SSD. I tried rendering to a third WD Blue drive that is storage only but it didn't make a speed difference either way.

My full computer specs are as follows:

ASROCK Extreme4 Gen3 Motherboard
Intel i7 2700k @4.2ghz
16gb Gskill Ripjaw 1600mhz DDR3 RAM
WD Caviar Black 64mb cache SATA 2 HDD (boot drive) cached by 40gb SSD
WD Caviar Black 64mb cache SATA 3 HDD for FRAPS writing
WD Caviar Blue 640mb HDD for random storage
SLI MSI Twin Frozr III GTX560ti Core 448 1280mb Power Edition GPUs
ASUS Xonar Essence STX Sound Card
860 Watt Seasonic Gold Rated PSU
Windows 7 Home Premium 64bit

A friend of mine (and partner on Youtube) has SLI 560ti 3gb cards with an identical set up to mine minus my sound card and crushes my rendering performance (he renders 1080p in 1:1 time). The only things I have come up with in my research are that it may be the Vram difference and/or it's that his 560's are a different stock of 560's (the 448 core runs on a different board) that renders incredibly fast for some reason.

I use Sony Vegas Pro 11 64bit on Windows 7 Home Premium 64bit. Sorry this was so long but I wanted to try and make sure I gave all the information I have on the subject. I might have missed something so if you need any more information just ask. Thanks in advance!