Before you decide to edit your profile, which is pretty easy to do, make sure that your monitor isn't too bright, especially if it's an LCD. Try to calibrate it down to 100-110 cd/m2 and view your prints with a good D50 viewing light. If, after that, your prints are still too dark, then it's a simple matter to tweak them with something like Gretag's Profile Editor.
If you're talking about doing prepress proofs, then the Premium Semimatte is actually pretty good. I use that a lot myself, and while it's a bit whiter than most of the proofing stock that printing houses use, it's actually closer to the real whiteness of the paper we're printing on.
For doing pre-press proofs, you'll want to convert to your press CMYK profile and then back to your RGB Epson profile in order to simulate the press on the Epson. You have two options when doing the second conversion - Relative or Absolute Colorimetric. Relative leaves the whites alone and Absolute attempts to put the paper white of the press back into your Epson proof - provided, of course, that the Epson paper is actually whiter than the press paper, which it usually is. The only problem is that that white simulation is usually less than perfect and is something else that may need to be tweaked, and THAT tweaking is much more difficult than a basic overall brightness tweak.