You could really pick from the full range of core mats that we have (at the power levels your talking). Then it is a question of voicing... each sounds a bit different. The nickel adds a bit of warmth... but has good low level resolution... the M4 tends towards very good clarity and see-through... some of our customers really prefer the admixture of M6 and nickel (as a pinstripe) and feel it sounds best. We offer the range for you to choose from (knowing that it can be a difficult choice).
The nickel would be the most expensive... the pinstripe in btwn all nickel and all M6.
these tranneys are relatively small guys... so they come in channel frames with solder lugs. They have a single impedance secondary of 8 ohms.
Mike