Looking for more amp power for ACI Jaguars

I have the above monitors which are not that tough of a load (Nominal 8 ohm that dip down to 6 ohms), but they are relatively inefficient (87db). Recommended power for them is 50-300 watts.

I am using a TRL modified Musical Fidelity A300 integrated which is 150W @ 8 ohms and 260W @ 4ohms.

I have a rather large room (17x25) and my listening position is about 9 feet from the monitors with a good 10 feet then behind me. I do use a an ACI Titan sub for the low end duties. JAgs go down to lower 40hz per specs, but I have them plugged in rear ports so they roll off at closer to 60hz.
Although the ACI Jags do not strain with the MF A300, they seem like they could use more power IMHO.

I was thinking about adding a decent ($1000) used more powerful amp and using the preamp section of the MF A300 for now. I would add a dedicated preamp later (likely a tube pre) and sell the MF 300.

HAve looked at the MArsh 400 amps on AG here, a used Parasound HCA 3500, and a few others.

Another option is bi-amping but I don't quite understand how that works and how to then match gain levels of amps.
I do bi-wire the Jaguars with positve results.

Would welcome any suggestions.