I am about to start construction on a Falcon 56 Mk II I picked up through the forums here. The kit looks as good as I remember the old Goldberg kits looking. The parts just about fall out by themselves from the die cutting and the wood is excellent. The only downside to the kit is it looks like it has passed through numerous hands since it was new. Everything is there (with a few extras) but someone punched out all the wing ribs. Not usually a problem but when they did they snapped off the jigging tabs. A bit of a pain to recreate but not a disaster either.
Sorry I prattle on.
I have both a .46 AX and an old Webra Blackhead .40 on the shelf and I plan on trying the model with both (no... not at the same time) I am convinced the old Webra will be enough engine for it. My Skylane 62 flew like a charm with it.
Bottom line on engines is, use what you feel comfortable with and what you can access parts for quickly at either your LHS or mail order. Nothing irritates me more than a perfectly serviceable aircraft grounded while you wait for a $5.00 engine part. (or any other part for that matter)
Another consideration is run time. While I love the .46 for it's reliablilty and power, it seems to love fuel. The smaller engines listed in this forum should give you adequate power and longer flight time without having to shoehorn in a larger fuel cell.

I have never owned a Falcon 56 before but I have seen many of them fly over the years. That was why I went looking for one. They are terrific flyers.
Whatever you decide. ENJOY!!