He's made a decision on his preference. He want's suggestions on a hi-cap 10mm longslide. What's wrong with that? Maybe it's not what you would want, but it's his decision and we should respect that.
That said, and STI 2011 was the first thing I thought of. And the price tag is no surprise. STI makes some very unique guns, and people pay a premium for them.
Another option is the Fusion Grand Sport Wide Body. It's a double stack, 6" 2011 style, available in 45 acp, 10mm, 40 S&W, 400 corbon, 9mm and 38 Super. It uses the STI mags.
It sells for $1795. Fusion Firearms