I *really* think this is a purchase you need to do together. The setting you're looking at is....a whole lotta ring - and not to everyone's taste. Most women prefer a more delicate setting with a lot less metal. Your GF may have expressed an interest in a larger setting to compensate for a smaller stone - and for no other reason. A 2ct stone, however, can carry a ring with no need for support. Also, a more elegant engagement ring can get the same effect as the ring you're considering by adding a blingy diamond wedding band. That way she can mix and match and have more options. My sincerest opinion is that the Tiffany setting will date - and date FAST, since it already looks somewhat out of fashion to me. It's a very specific look, and very specific looks go out of fashion inexorably. You're better off to go for more of a classic if you don't intend to upgrade later.
I completely support your decision not to upgrade down the track. However, opinions change. When I was engaged, I NEVER thought I'd upgrade - yet here we are. So make sure you go with a company with a good upgrade policy. And if you DO 'never upgrade', you really need to hit it out of the park first time - which brings us back to my first comment, which is that this is a purchase that needs to be made together.
This has to suit HER 100%. It really doesn't matter what you think of it. Involve her in the process; it's the best way of protecting your investment.
ETA Having said all of that...that Loupe Troop stone is a stunner for the price - what a deal!
Thanks for your advice Mrs. B, I have concerns about the Loupe Troop stone. Everyone here is recommending it as a stone that 2ct above with great cut and clarity. My issue is buying it with a "all sales are final" attachment. As a novice buyer it intimidates me dropping that much money on something I don't get to see in person and have no way of returning. Plus I can't help but feel "what's the catch?" Why would a diamond that is so nice be so cheap?
Would you recommend like other posters said go for a simpler band and just a bigger diamond then?