Always start with the belt. I'm personally partial to the Looper Kydex reinforced belt available through BladeTech and
http://www.unholstered.com, but there are many other quality belts out there from the Beltman, Kramer, Tucker and Wilderness just to name a few. Some people swear by Galco belts but I've personally had bad luck with them, the one I had stretched out badly in only a year.
Another thing to think of is the width of the belt. I prefer 1.5" since that is the widest belt I can fit through the belt loops on all my pants. If you wear a lot of dress pants you'll have to check but most of those are 1.25" belt loops. There are 1.75" and even 2" belts but those generally won't work for anything other than Jeans and workpants.
IWB holster: I have an MTAC by Comp-Tac I love for my Glock 21 and a Quick Clip from Sideguard Holsters for my Taurus 650 revolver. If I were buying another IWB for either of those guns it would probably be a Double Clip like Strad posted earlier for either of them.
OWB Holster: I have a Double Snap from Sideguard for my Glock that I use for competition but really have my eye on a Bianchi Carrylok for it. I've seen guys put full size 1911s in them and they conceal better than most IWB holsters.
Bottom line, there are very few holsters which would be less concealable than a Blackhawk but there are some OWB that conceal very well and some IWB that are very comfortable. It's all about personal preference.
"The democracy will cease to exist when you take away from those who are willing to work and give to those who are not". - Thomas Jefferson