Heights Vinyl (ha ha - I've never been there, and have heard they have an annoying color coded pricing system, so uhh sorry if you hate it)
Sound Exchange
Bars and venues:
Poison Girl
Rudyards (gigs too, sometimes of Termbro interest) (has decent pub food too)
Mangos (gigs too, sometimes of Termbro interest)
Grand Prize
Walters - for gigs (not really a bar, per se), sometimes of termbro interest
Eats:
Cheap and amazing - Les Givrals for Vietnamese sandwiches
La Tapatia for Mexican
Lankford grocery for ridiculously fattening, gnarly hamburgers and amazing mexican and comfort food daily specials (cash only)
Avoid barbecue places - they all suck
Burger guys (but it's kinda far outside of the main inner part of town - Houston is a very huge, decentralized metro area, much like Los Angeles)
There's tons of Pho places, but I'm not super knowledgeable about which are great, etc.
Umm, there are tons and tons of restaurants in Houston, of all pricing levels and I"m not sure what you can or want to afford, but some higher priced fare:
Uchi
Dolce Vita
Hugos
Vinoteca Poscol
Too bad you won't be here in early October - some decent gigs going on then. Nothing is popping into my head for early September gigs.
Rothko chapel and museum as said before.
please bear in mind - I am a 47 year old, sorta out of touch old guy so I may not be that helpful here.