Currently I have 2 ADSL lines (one per each BM server)

Is it possible to have some sort of line concentrator (making 2 looking as

Due to a single default gateway it is not possible (as I understand it) to
have 2 lines attached to a single BM server (unless dead gateway is used -
not really what I need, I need to have to lines constantly used)

I tried Xincom Dual WAN router, but could not get this thing to work after
hours of trying