MBOX 3 compatible with other preamps??

[Maddern]

Hi Folks,
I'm looking for some insightful knowledge.... to be frank, having bought the MBOX 3 to compliment ProTools of which I bought over a year ago but have still to get to grips with (work is busy and I'm still doing most stuff on Cakewalk).. I'm disappointed with the quality of the Mbox as a main preamp, but would like to use it as an interface into ProTools... I'd want to stick with my tried and tested Behringer (yes, Behringer) Ultrgain Pro... as it has a much better sound, warm and nice depth (great value bit of kit)... so logically, I'm connecting my Utragain preamp into the MBOX at the front, to channel it through without using the Mbox as a preamp.... well.... horrible.... there's a constant static, that no matter what I try, it's always there once the volume is raised on the Mbox.. even when the Ultragain levels are completely turned down... the cable I'm using is of a good quality... so it must be a compatibility issue.... can anyone out there give me some advice... am I doing something wrong, or is it simply that AVID doesn't want the MBOX to be used with any other preamp set-up? I'm desperate to start using ProTools, but what to do?... use the inferior sounding MBOX?... or is there another preamp set-up I can use... maybe I have to sell and make a loss on the Mbox buy?.. I've got ProTools9, but have not been able to connect anything other than the Mbox in this software? PPPffffff... any advice is really very welcome!