TSx vs. Signature Series

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Hey, everyone. Looking for alot of feedback on this. This is a two-part question.

So first, the upgrade bug has me again. I currently have a complete Polk TSx set-up: 550t's for the front channel, two pairs of the 110b's for rear and front height, and the 250c center (with a Def Tech Prosub 800) all driven by my Yamaha RX-A3080. I really like that set-up but have always felt like there was a veil in front of everything. I have become really interested in the Signature series, mainly the S60's, S15's, and the S35 in the same configuration I have now. Locally, alot of these speakers are about 50% off right now! Is it worth moving on from my TSx's to go with the Signature series? I know there are much better speakers out there, but for the money, do the Signatures deliver better than the TSx's?

Secondly, in reference to the Yamaha 3080 and the 550t's, can I safely 'bi-wire' them with the remaining two unused channels? Will this help the 550's open up even more? Really appreciate it.