The XA300's are a powered speaker and good for using with a PC. How would you feed either the Q100's or LS50's?
As for value, it's a tough call and largely subjective. The XA300's aren't the later wireless version so value suffers a bit more. Don't beat me up but I'd be surprised if you could get more than about $400-$450 for them, if even that. It's going to take the right buyer to appreciate what they are.
Assuming you have some kind of amp, you'd find the LS50's to be a couple steps up in every way over the XA300's. The Q100's would be a little better than the XA300's because it's the same Uni-Q driver in a better, ported cabinet. What are you ideally trying to achieve and how much budget can you apply? If you want the best 2-channel music for right now, the LS50's with a Bluesound Powernode would be a great start. The Powernode 2 has a subwoofer output, the original (now can be had well under $500) doesn't. Later, the LS50's would deliver more from a higher quality, more powerful amp but a Powernode or Powernode 2 gets you Tidal Hi-Fi (including MQA full decoding) streaming and some other inputs for relatively cheap.
KEF R500, R200C, R100, SVS SB2000 sub, NAD T758 receiver, Pro-Ject RPM1 TT w/ Sumiko Pearl, Bluesound Vault2, Sony BDP-S480 BlueRay player, Samsung UN55JU6500F 4K LED TV, KEF M500 headphones, Sony CDP-CE500 CD changer.