Vandersteen 2CE amplification jumpstart-cables,sub

I have the Vandy 2CE s and they seem to need a little more kick to drive them. Right now I've got a pair of Quicksilver Silver 60s w/ EL34 tubes but the bass and "drive" seems a little lacking ?(esp. w/ phono). I've been thinking about the following approaches, but don't know which will give me the best bang for my buck:
--I could switch out the EL34 tubes for KT88s.
--I could upgrade my Audioquest Midnight 2 speaker cables.
--I could add a Vandy 2W sub.
--Are the quicksilvers a good match for the speakers?
I'm using an AR SP16 preamp.
All suggestions are greatly appreciated.