should i go with kt150's now or wait a bit??

simple question folk's,    I have two jolida 502 amps running in mono.  kt120 tube's with about 200 hours. just broken in lets say.  this is almost going on two years now so I guess Im not listening as much as I should be. I will take care of that!!    the amps are running the top end of my infinity 1b speaker panel's.   mid's and high's.  no bass work here. so the question is is it worth installing kt150's at this point in time.    for $600, I would need eight of them, what kind of improvement in sound would I get.  with just 200 hrs on 120's would you run them a little longer to at least get some use out of them.   everybody like's the 150's for the solid bass they get out of them but I would not see that running the mid/tweeter panel.   what would you guy's do if you had the $600 ready to go??  (don't answer that)   can we assume in time the 150's price will drop a little more and just wait it out .   I know it's such a tough decision here, just help me out ok. thanks