I did a build project this summer. c90 + v30 = epic win. Now that I have tried it, I'll give it another positive vote!!! GREAT for hard rock and metal. I'd put them in a mills Mach 212B or my version of it. Check out my second build thread in this forum if you want to see what I did.
With the close back / baffled cab it really helps a Dual Rectifier come up with a serviceable lead tone. Additionally, you get a super clear, phat, and beefy crunch tone. The cleans are good but not the same as an open back cab. Definitely do the job.
As for the speaker combination: The v30s provide the crunch and the c90 provides the beef, girth, and lead thickness.
I also find that the low mids and muted highs of the c90 mesh well with the upper mid spike and ice pick highs of the v30. The result is one of the most balanced sounds speaker combos possible.