Sounds like the OP already made up his mind, but I too put a 4.5-14.5x40mm Nikon Buckmaster with SF on my 17hmr. I find I really can't see these small 17cal holes well... below about 14x @ 100 yards. 16, 18, 20, 24x would be even sweeter of course. For most of my varminting, I would probably put 16 power at about my minimum now, where I like to walk around dialed down to 9 or 10 but where I also like to target shoot/group test the different brands of ammo then. The little HMR has the ability to strike out there pretty far. Accurate, fun & potent round, so I decided to give it more than 9x.
For ground-hogs, I would limit your shots to about 125 yards. And you are definitely on the right track making them head shots or at least good solid upper body shots (neck, heart/lungs.) My varmint heavy barrel liked the 20 CCI Gamepoints better than anything (except the S&B V-MAX which they don't make any more). For ground-hogs, I would rate them 17 TNT's as BEST, then V-MAX, then 20 Gamepoint / XTP's, with the FMJ's being pretty much useless for anything other than headshots on squirrels maybe. The 20's penetrate like crazy, but I think may pencil through the animal a little too much.
Whatever glass you end up with, you should enjoy this new toy! A little light for ground-hogs IMO. I take the 22hornet, 222, 22-250, 243win out after them now, and just enjoy plinking with my hmr as my faster, more accurate 22. ;D