To answer your question more directly and simplicticly; yes, all three tubes are of the same tube family and are different denotions for essentially the same tube (IMPORTANT: the same tube designs by different manufacturers will have distinct sonic-fingerprints though that will sound quite different when utilized different hardware...and to different ears! In other words one brand M E88CC will not sound the same as another brand T E88CC). Two more for that same family would be 6DJ8 as well as E88CCa. To learn more, check out Joe's FAQ as Newbee suggests or just search the archives here and on AudioAsylum ("Tubes" section) with your specific questions. I'd also highly endorse Creepers recommendation for Jon at The Tube Store for sound advice and good customer service.
Have fun!
Marco
