Need a new Amp Rig, and some help from the experts!!!

[mysticalcracker]

So, I am fairly new to playing bass. I have been playing guitar and drums for ever, and have fallin in love with "the low end". Right now, I am playing my friend's 80's American P-bass, I'm not sure how to explain the pick up setup, but it has both p-bass and jazz bass pickups, and they are lace sensors(Active), but I guess all lace sensors are active. Anyways, I am playing into my fender bxr-100 that I got for $85. Now it is time to upgrade my amplification. I am most concerned with tone, b/c I record a lot, and I don't need crazy amounts of volume, b/c at this point we are not playing out, However, I want an amp that could gig if I need to down the line. I am pretty sure that I want to go tube, and the Hartke 5500HA looks pretty good, with its tube and ss preamps. Then the cab: I want a really low bottom end, but the Highs are important too, b/c I play a lot on the high strings. My budget is b/t $400-$500 looking for used stuff. Thanks for any input. I know I have a lot to learn, but I'm lovin every second.