Pre Amp with pre-out for Arjen Helder Ta2020

[Quba123]

Hi. I'm middle of the buildprocess of building an integrated amp using Arjen Helder TA2020. I use a pair of Tangent Clarity speakers but the problem is that my room is quite big so there is almost total lack of bass. The mids and highs are good tho. i have a velodyne active subwoofer at home that i would like to use with my T-amp becouse the sound from the arjen helder is excellent. So my question is if there is some good 2.1 Pre amp board or maybe a way to add a single pre out to the analog line level?

I dont want to change to tower speakers, and i dont want to change amp!

Thanks!