Hi guys, just puchased a pair of 604-8k drivers. I loaded them into a pair of 6 cuft bins tuned to 40hz. they sound wonderful, they came with 904 crossovers and are fitted with er-15 cones. I,d be interested to know what altec cone would be the sweetest sounding to use with a valve amp. The er-15 cones were fitted for hi power handling apparently. I'm looking at purchasing a Jadis "Orchestra" valve amp, 50 wpc. The transistor amp I'm using isn't doing the 604's justice.