Definitely upgrade the amp first. The amp you are using is, putting it in not so nice terms, crap. It may be fine to practice at home with, but there is no way in Hades you can gig with a 35 watt amp. The bass is probably a fine piece of equipment, but obviously doesn't fit you. I'd say your amp needs are more dire though.
Have you considered an amp somewhere in between? Perhaps you could save a little money by buying something smaller than an SVT with an 8/10, and use the extra to get another bass. For example, new GK 1001RB II can be had for $600, and they are a fine, powerful head. Avatar cabs sound decent and are very reasonably priced. There are alot of nice used cabs available for a reasonable price, Edens, Aguilars, etc. Either way, a 4-10 can cover almost any gig outside of extremely large venues.
Have you considered an amp somewhere in between? Perhaps you could save a little money by buying something smaller than an SVT with an 8/10, and use the extra to get another bass. For example, new GK 1001RB II can be had for $600, and they are a fine, powerful head. Avatar cabs sound decent and are very reasonably priced. There are alot of nice used cabs available for a reasonable price, Edens, Aguilars, etc. Either way, a 4-10 can cover almost any gig outside of extremely large venues.