I have the Revo Sx 6.4:1.  I want to buy a new reel and rod for crankbaits.  I'm thinking of getting the Revo STX.  It's gear ratio is the same 6.4:1.  Will this be alright?  If I use the pole for cranks and other application do I need a lower gear ratio?

depends on the cranks you're throwing...don't believe it matters on the weight of the crank you're throwing as much as it does on the size of the lip of the crank you're throwing.

bandit 200, dt6, cb200 can be done with a 6.1 easily.

dt10, cb350, poe's 300, you're better off with a good 5.1.

you can do a dt16 or a poe's 400 on a 5.1 but, a good 4.1 will do it better.

i hear a lotta guys on a lotta boards say they use a 6.1 for all cranks and they just slow down.

pull a poe's 400 all day long and they'll change their mind.

imho.

If you decide to buy a "dedicated" reel,  a gear ratio of 5.0:1 would be a much better choice.

8-)

I would go with a 5:1. I first bought a 4:1 it was too slow for me and I returned it for a 5:1. I found the 5:1 to be a good speed even for the deep divers such as the DD22.

The only 6:1 I use is for burning lipless cranks back to the boat.