If you can, please give this benchmarker a run.

It's a simple little tool.
Unzip it, run the .exe, and watch as three "Bloke" sprites circle around for a little while.
Don't touch anything. The benchmark tool will do it all for you.
Running through a bunch of sprite-pushing tests, blending methods, and audio streaming, too.
It'll also flip to fullscreen to check there, too, so be warned if you're watching any other media on your PC at the time!!!

Once it's done (about a minute and a half) it'll leave a debug.txt file, which you should send my way.
Thanks for testing!