I've never seen a tank over 30 gallons sell for anything less that 100 bucks. If your getting equipment w/ it, I'd plan on spending $450+ probably more. If not, $200+. Also, you can buff out any minor scratches on the outside and ones on the inside don't matter since you can't see internal scratches when water is in acrylic tanks. Any tank that has those demensions, especially acrylic, I would buy at pretty much whatever cost you can get it for. That sounds like a sweet tank.
I have a 60 gallon acrylic if that's largish enough and it's better than any glass tank I've ever seen.