G15C's in my Hiwatt 2x15" cab

Running a 1975 Peavey Classic (50 watt) 2 x 12" combo (stock Peavey speakers.....not black widows) with a 70's Hiwatt 2 x 15" as an extension, loaded with G15C's. These speakers are pure magic. Nice lows and mids, and so crunchy when you throw some drive into it. Amazing at high volume levels. Very very warm. 

Problem now is that the stock Peavey speakers in the combo are WAY too raspy and harsh (as compared to the sweet singing the 2 x 15" does). Anybody have any suggestions as to a Warehouse speaker that would fill out the top end in the combo nicely, without sounding obnoxious? I play mainly a high-volume psych/punk type style (think Chrome).

I absolutely LOVE your speakers,

Myke Adaptiv