I saw this on ebay, might be a consideration to stick in front of the eTap2hw unit...........
http://www.ebay.co.uk/itm/330768781286?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
There's a similar thing from Behringer;
http://www.ebay.co.uk/itm/BEHRINGER-Tube-Ultragain-MIC100-Valve-Mic-Preamp-NEW-/130804511261?pt=UK_Musical_Instruments_Outboards_Effects_MJ&hash=item1e748e721d
And for the tatter-abouters;
http://www.ebay.co.uk/itm/251195017347?_trksid=p5197.c0.m619
Ecca