Which Martin guitar to buy?

Hey guys, I've asked this question today already, but I'm trying to
get lots of options. I've been playing guitar for a while now and I
usually buy $500 Fenders and such. But I've decided to lay down the
money and nice Martin for around $2,000-$2,600. I've been looking
around and I've found a few: D-18, HD-28, and the GPCPA3. Any thoughts
on those guitars? Also, if you have any other guitars in this price
range to recommend, that'd be much appreciated. Thanks!