RBX270...great bang for your buck...I have a RBX170 (passive version of the 270) and think it ROCKS! I paid about $130 US for it (delivered)...it was used, but MINT.... I've heard that spectors have issues with their bridges...a BEAR to setup, is what I heard...I've had no probs with the Yammy...
Well let's put it this way, I LOOOOVVVVE the tone out of my Spector Legend 4 string, but yes, the bridge is scary and I only have it strung by professionals. So, if that's any help...
I don't know what Spector bridges you've set up, but the ones I've owned have almost been dead on. I've only had to do minor adjustments. As for the Spector NS2000 series, the bridges should be straight forward since they're of lesser quality. If I were you, I'd buy a Spector Rebop. They're a Euro bolt on that costs anywhere from around $550(ebay) on up. Bass Central is having a sale on them right now with 4 stringers going for $699. Great instrument without breaking the bank.
I did play a spector rebop, at least I think it was as it was a bolt on and built in Czech Republic or somewhere like that. At any rate...it was a good instrument...nice neck, good tone...a modern tone with a bit of growl...not unlike some warwicks I've tried...but they wanted like $1500 Australian for it...(no thanks)...sorry but there's no way that thing was 10 times better than my Yamaha...in Australia, bass-on-a-budget is not such an easy thing.
IMHO you should play all three and then decide. I have and for me the Spector is the better option. I prefer the neck and the sound over the other two.