To be honest, for an old TM AK47, if it's ex-rental, about £50 is a nice price to pay, £105 is a bit much IMO. A tenner on the other hand is just ridiculous.
TM AK series tend to be fairly quiet in a sense, I think though it's more that they have a different sound to most guns; a lot of AEG are very "snappy" in their sound, whereas the AK series tend to be a bit more "woody", if that makes any sense at all, if anything it makes them harder to hear at range, mostly because they sound further away than they are...
Interesting project you've suggested, I quite like the idea of the paintjob especially - it's going on the "serious contenders" pile