Ya, a 75 gallon tank is a nice size, I loved my first one. Gives you considerably more stocking options than the smaller ones, even a 55 for that matter.
I was sort of happy to find a good deal on a used 125 (6'x18") right after Christmas last year, finally had a decent size tank for my growing severums and silver dollars that had just about filled a 75.
Finding the 220 a few months ago was the kicker though, 7'x2'x2' is actually big enough to satisfy me. I no longer search craiglist for more tanks.
One of the good things about having multiple tanks is that setting up a new one is much faster. I just swapped filter media from a couple of 75's and added fish.