The main thing about suits is that, wherever you are, they should fit you. If you can buy a cheap suit that off the peg fits you, you'll almost always look better than if you wear an expensive bespoke suit that was made for someone of a different build.
Going up the scale of Mens Wearhouse, Brooks, Zegna etc. what you're getting is not only fabrics and tailoring but choice in style. American cuts tend to be straighter and baggier while European cuts tend to be more shaped. If you have a reasonably square build (e.g. the "football player" build) then you can probably get away with a traditional cut. I'd go for Brooks on the basis of fabrics and build quality - the investment will pay off in the length of time the suit lasts. If you are a smaller or slimmer guy (e.g. the "runner" or "swimmer build") or if have difficulty getting clothes to fit, then you may be best to go for something in a European style. I don't think you have to go all the way up the price range to a bespoke Zegna for that, but you may have to hunt a little more.
The other thing is that you can spend more money for fabric (Super 120's, 140's etc.) that are more fragile. Better to wear a series of hardwearing cheaper suits than an expensive suit that has holes in it. Better still, wear suits in rotation and keep the fragile suits for important client meetings rather than the days you'll be dashing around town.
There are some good general tips on suits from the US perspective on the GQ Style Guy website. Another useful site for an introduction to bespoke tailoring is englishcut.com.