Threshold verse Pass Labs how can I justify significant price difference

I'm running currently series one Threshold S500 with the optical bias and Threshold S500 second series as a bi amp config to my JBL 4367. System sounds the way I like it no complains.
Now I've been having thoughts about upgrade amps to Pass Labs 350.5 or 250.5.
250.5 would be in same power range as S500 so my question is since Pass will be priced higher how much better would it sound and is it worth to spend extra $$?
does 250.5 will make so much difference that there is no sense to go up to 350.5? or the only way to get any significant upgrade is to go for 2 of 350.5 and would it be so much better sound than my Thresholds I could justify spending extra $7K!

Can't wait to hear what you guys have to say.

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Valid point and all opinions lead me to conclusion to stop improving my setup and start enjoying it.  All doe I always wanted FAT 10 both panels so I just might get it and see if on pre amp stage I could improve situation 
Get the the Pass and find out for yourself. You can always sell it, if its not what you seek. But I am sure you will be wondering what the hell the people in this thread were talking about.
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