I'd go for the Dakota myself.......Nice aeroplane to fly, plenty of power, no wobbly gear to worry about (or forget). I prefer it to the TB10 which is a bit under powered but a comfortable aeroplane and nice to fly (good cross wind).
A real go-places machine would be a TB20 but you'll be lucky to pick up a good one in your budget....
There is not much difference between a PA28-140 and PA28-180, the 180 is a few knots faster but IMHO, and no offence meant, just as boring
. If "upgrading" to another PA28, I wouldn't even consider anything less than 200HP. I would consider a 200HP Arrow, the retractable gear add a few knots to the speed but at increased maintenance costs.