The easiest thing would be if the Arcam had pre-outs for any / all channels - then you could put them out to dedicated amps for any / all channels. I'm assuming the Arcam doesn't have these, but if you haven't looked and it does, the problem is easy to solve.
Most prepros should allow for configuring which speakers you're using and which ones you aren't, and routing whatever decoding mode you're using to the available channels. So, if you're using DD 5.1 decoding, but there are only 3.1 speakers, all the sound will be sent to those 3.1 channels.
There are many prepros with analog bypass mode, older models as well as new, that would accomplish the prepro side of the equation. Then, of course, you'd need amplification for your fronts.
The Dyn 1.3SE will appreciate all upgrades to amplification and ability to deliver current. That's a nice pair of speakers, but they do love their amplification.
Most prepros should allow for configuring which speakers you're using and which ones you aren't, and routing whatever decoding mode you're using to the available channels. So, if you're using DD 5.1 decoding, but there are only 3.1 speakers, all the sound will be sent to those 3.1 channels.
There are many prepros with analog bypass mode, older models as well as new, that would accomplish the prepro side of the equation. Then, of course, you'd need amplification for your fronts.
The Dyn 1.3SE will appreciate all upgrades to amplification and ability to deliver current. That's a nice pair of speakers, but they do love their amplification.