OK, I decided to go for a Dr. Bass Rx115 3 space "airhead" cabinet to house my RBI pre and Carvin DCM1000. The cabinet comes stock with an Eminence Beta 15 350watt driver rated down to 35hz. The Dr. offered a Delta 15LF 500watt driver rated at 40hz on the low end as an upgrade +$25. I will be using a 5 string and pushing it hard. Is the Delta 15LF a worthwhile upgrade? The specs confuse me on the low end. It seems the Delta will handle more power and has greater excursion while the Beta is rated to go 5hz lower and is supposedly more "musical" sounding. Additionally, the Beta is recommended for a min. box size of 3.75 while the Delta is suitable for a smaller box, min 3.25. The actual cab is 18"hx20.25wx15"d. Help me decide! Thanks in advance.