A pair of either Gcons or Icons would work very well with a BC3500 @ 2ohms.Do you have any idea what you might want to upgrade to later on? If you're interested in adding another pair of subs someday for a total of 4, either series of subs would be a great choice in my opinion. You could run a pair of D2s now @ 2 ohms, then add two D2s when you're ready and wire the amp down to 1 ohm. If everything is done right, it should be "clean and loud" either way. well with a 3500 you could comfortably run 2 xcons in the future. just saying. thatd be at 1ohm load tho.