I don't know if you guys need any more shops to visit. I am a graduate student at Baylor College of Medicine and I've hit just about every card store in the greater Houston area.
Houston Sports Connection is on the West side after the Beltway 8 on Westheimer. Selection is ok but i think the prices are a bit high on the wax side. Good amount of supplies. They may work with you a little bit on boxes (5% - 10% off sticker) but the prices are pretty high.
Odyssey Comics and Cards i've only been to once but the guy worked with me and sold me the rest of 09-10 UD Basketball packs (i think 9 packs for a total of $30 and still got 2 GUs and an auto). Very nice owner.
On the east side of Houston near the beltway is store called Sportscard Shack run by a nice Filipino guy. It's a small shop its with a lot of the recent sort of brands for baseball, football, and basketball. Not the biggest selection but enough. He can work deals with you too. Lots of kids go there to play gaming cards and stuff.
On the north side of Houston, there is a flea market called Armadillo Flea Market on I-45 north just exit Airtex. If you enter the front left entrance (i think it used to be a garden ridge) go straight back and you'll find a lady who sells action figures, jerseys, and a small selection of wax. I think I bought most of the basketball boxes but i remember there being 2002-03 SP Authentic bkb and a fair amount of football/baseball as well and singles/memorabilia. She works the booth and the owner is a retired cop i think and she can call the guy to see if he can knock the price down on some boxes.
The one card store I highly recommend is in Alvin, Texas. If you take 288 South to Highway 6 and go east to Alvin, and get onto Highway 35 bypass south and take a right onto E. South St. The store will be not much further and to the left. The sign to the store has been busted but this store IS WORTH THE DRIVE! It's called The Old Ballpark and this guy has some an amazing variety of sports cards and boxes. If you are really into basketball, he has tons of late 90s stuff. He has good selections of baseball and football as well as gaming stuff. This is by far the best card shop in the Houston area. If you are UH it's probably 30 minutes to get there. The guy really knows a lot about sports and there is usually 10-15 guys there on breaks chatting, talking sports, and/or busting wax. He gave me deals on some boxes and card supplies (sleeves, toploaders). I highly recommend going there.
I hope this was helpful.
Collecting all Houston Rockets players, current and former.