You might be better off asking that Q on the Guild >>
http://www.guildwargamers.com/phpBB3/index.phpAB and SHQ do fine together, SHQ being on the thinner side. Not sure what you mean with AB vehicles as they only make figures (hence AB Figures). You can get the vehicles in plastic, metal and resin, in all price ranges, from simple to frustrating. Fantassin and Combat go not too shabby with those btw.
As for Moderns, rather pointless going to RH Models/Liberation for Modern West Germans as the entire range is unavailable and service (if you can call it that) from Rolf is spotty at best....I'll leave it at that.
Wartime gives you quick service, and be sure to look at Elhiem too, fast expanding ranges. SandS have jumped on the figures bandwagon as well, they make a ton of vehicles for modern and WW2.
But like I said, visit us over at the Guild. Tons of eye candy, just as helpfull as here but more focused on the wargaming side of things.
If you need a hand with anythinbg, let me know.
Wayswatcher here, Gunbird on the Guild.