I've not done that, but, a thought is there are loads of old avants out there  being sold for next to nothing because the screens have gone - but the power amps might be able to be reused and built in? - perhaps find one and use the amps?

I suppose though the Beolabs amplifiers are designed specifically for the drivers, cabinets and cross overs they are built into, Beovox thoguht will give you a much wider choice of power amp

Not that easy! You could of course take the Penta route and simply get some Beolab 200s and drive the RLs with those. To make them properly active would be quite an undertaking as you will need active cross overs and I suggest it is too difficult to do - unless you have access to a frequency analyser etc!

purchase some ICEpower amps.

The Avant idea is good but looking for something with more power. And yes i got to thinking about the active cross overs that would be very difficult if not drive me nuts lol. though going with the beolab 150 or 200 is an idea i have been thinking about sadly i never really see them for sale. right now i have the RL 140 in the bedroom with the beocenter 9000 and they are doing nicely lol but more power would be nice!!!

A pair of damaged Pentas could be donors - as long as the amps work. Otherwise a bridged Quad 405 for each could be interesting!!

yes belab140 or 200 would be nice to have for them or a pair of Pentas would be nice too 🙂