You can put lenses in that mask, but we prefer to sell the Splendive II or Splendive IV masks for lenses. Multiple reasons here. One, they are easier to get in and out with less chance of cracking the frame. Also, the Splendive II & IV use bi-symmetrical lenses, which means there is no left and right. This has an advantage for us in that we only need to stock -1.5, -2.0 etc... not -1.5 left, and -1.5 right, etc.
They do not have .25 lenses, just -1.5, -2, -2.5 etc... We've found, when in doubt go up, so you'd do 2 lenses, both -1.5. Unless of course you wanted them custom ground - then you can do anything, but the price goes up.
The advantage to you for bi-symmetrical lenses, is lets suppose your boyfiends eyes both weaken slightly. Now he'd take a -5.5 in one eye, and a -6 in the other, but if his eyes got a little worse, you can move the -6 over to the other side and just buy a -6.5. This saves you money later over having to buy 2 more lenses.
But yes, we have gotten them for the liberator plus before - but with the advantage of the bi-symmetrical splendives, we don't stock them for the liberator series.
And with your SB discount, you're looking at under $100 for either mask with 2 lenses.
http://www.scubatoys.com/store/detail.asp?PRODUCT_ID=TusaTM7500Q
Hope that helps!