First, that is NOT a slut dress! It's gorgeous.
Back OT - I think comfort and slightly matching your level of dressiness is a great plan! we're not doing
DCL, but DF just bought a really nice new pin stripe black suit (also from Men's Warehouse)... he has a card with them and every month gets a discount coupon (15%) plus for every $100 you spend there you get a coupon for $50 off... DF just bought 2 new pair of dress shoes and some new shirts for work a couple months ago, so he had a -$100 coupon... so, we got an awesome Jones New York suit (regularly $399) for -$100, -15% and an extra sale of 5% for using his credit card with them. It was freakin' awesome. We also bought the groomsmen matching dress shirts, ties [which were buy 1 get 1] and pocket squares. Anyway, we started out thinking tux, but what the hell

for a little extra, he could get a suit that he can wear again a million times. Plus, he doesn't have a black suit (olive, blue, you name it, but not black - go figure!) He also got new dress shoes ... I was so excited...
It's similar to this, but I couldn't find the exact suit...
3 ties (originally priced $20)
3 dress shirts (originally priced $50)
1 new suit (Jones NY) (originally priced $399)
1 pair black dress shoes (originally priced $50)
3 silk pocket squares (on cards) (originally priced $10)
------------
with summer sale, coupons, and discounts = $450

Total steal. I felt like we robbed the place!
Plus, it took us all of 30 minutes. unbelievable. I wish my dress was that easy!! Guys are so f'n lucky.

jerks. it will probably take him 20 minutes to get ready too!
Anyway -- I can't recommend men's wearhouse enough. Plus with their huge summer sale they have a lot of sport coats (casual) on sale... maybe check out a pair of khakis, a polo and a sport coat for the ceremony - then when he takes it off he can be more comfy but a little more formal for your vows.....
JMO