Do I upgrade my Cerwin Vegas S1's from the 70's

Johnyd,You are probably not going to get much response here because you mentioned Cerwin Vega and this is a bit of an elitist site.Unfortunately many of the more recent Cerwin Vegas are pretty crude devices in a loud and bass crazy sort of way.Some of the older ones were quite good however and you may find that the fullrange type drivers lack bass extension, although like the Cerwin Vegas they are efficient and dynamic.Even things like the highly praised Zu Druid have very little bass below 100hz.
If you are wanting to build your own speakers I would suggest looking into some of the excellent kits available from suppliers such as Madisound,Edgarhorns,Parts Express and Zalytron.Even though your amps are quite powerfull I would recommend selecting kits with sensitivities above 91db/watt because valves and efficient speakers synergise so well.

I'll bet the EarthQuake soundtrack would be awesome- remember when it was roadshowed in first run, with monster CW woofers installed? :)

Johnnyd,

One thing you can do, prior to moving on to new speakers, is upgrade the speaker crossover. This makes a profound difference in the performance of a speakers across the entire frequency spectrum. If you want more information about it, drop me an email.

Mike

Johnny You have what are probbably the mostb efficient bass pounding speakers that have ever had the pleasure of being in a house.I know I used to have a pair,and speaking from experience,KEEP THEM.I sold mine and regreted it ever since.Even compaired to my Klipsh La Scalas, I would trade in a heartbeat.Hope this makes your decision easier. C Dude