Hey there, I know there is plenty of data regarding this subject but I am currently upgrading my audio system and need help doing so.

I own a F56 (cooper non s) without h/k or an amplifier for asd, I already replaced my front speakers to and I got a Gladen subwoofer as a gift (I think it is the SQX 10 VB or the SQX 12 VB), it barely fits the F56 trunk.

I think as a start, I want to get a 4 channel amplifier and connect it to the front speakers and the gladen subwoofer (bridged), and if it won't suffice I will buy a mono amplifier and two rear speakers and will use the mono amplifier for the subwoofer and the 4 channel amplifier for all 4 speakers. (In both situations, the underseat subwoofers will be disconnected).

However, I have a few questions:
1. My speakers are rated 50w RMS, and I saw online passing the speakers RMS is not recommended as they might burn, and if I bridge two channels my subwoofer will get only 100W, will it be good enough or should I go for a mono amplifier right away? I thought if I am wiring an amplifier I better be getting a 4 channel one and connect the speakers too to benefit from it.
2. I couldn't find a custom harness adapter to add an amp for a f56 (only r56), closest I found is Install a DSP Amplifier behind Dashboard – F56 – Base Audio (instructions on how to make your own harness adapter), which seems a bit of an overhead. If someone knows add-an-amp for the base f56 I will appreciate a link. (also, I have the andream carplay mmi and need to make sure the harness will work with it, as it already modifies the harness)
3. Should I get a line output converter with it or just an amplifier that supports speaker level input and alter the wires to the front speakers from under the seats? I think I do want an install that can be easily uninstalled and modified later.

Thanks and sorry for my English