Tranhu hi, looking at this impedance/-phase angle graph, your speaker are not easy but not as hungry as some.
You need and amp that can supply good continuous current from 20hz to 600hz which is all of the low and upper bass.
Big push pull tube (>120watts) will work but need a good output transformer and a 4ohm tap. Stay away from SE amps, OTL amps, and amps that only have 2 x 6550 or similar tubes per channel, you want at least 4 per channel.
Or you can go for a good quality >100w solid state, BJT (Bi-Polar) output or second choice Mosfet output.
http://www.stereophile.com/images/archivesart/708Revfig01.jpg
Cheers George