You might get more responses in the Monitor Audio Owner's thread.
There is no "RX10." It's called the Silver 10. The RX series is old and has been replaced by the "Silver" line. Silver 1, Silver 2, Silver 6, Silver 8, Silver 10.
If you have a subwoofer, there is no need to get the Silver 10 over the Silver 8. So it should be the Silver 8, or even the Silver 1, that you consider from that range.
In the Gold range, I think the same could be said: With a sub, there's not much advantage of the GX300 over the GX200.
With the money you save by considering the GX200 or the Silver 8 instead of the GX300 or the Silver 10, you could get a second subwoofer or upgrade the one you have, if appropriate.
The Gold range sounds better by most accounts, and certainly has nicer looks, but whether that's worth the extra cost is something only you can decide.
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