best use of my two ISP’s available bandwidth?

Hello,

i’ve been struggling with a microwave link of dedicated 512 kb down and 256 up. this link has unlimited quota though needless to say my 25 users tend to max it out.

i’ve acquired a new corporate dsl with shared 2mb up and 2 mb down with limited quota.

i’m going to setup policy routing table..

though i’m a bit reluctant to which protocols destination should i set on either one of these links!

my initial thought is to set critical protocols on the microwave dedicated link as it’s 100 % stable and provide 100 % bandwidth ..
though if that’s the case, port 80 would be destined to the corporate DSL link which would overshoot my quota.

any advice?!