Tonyrjkdavis

Hi everyone...first time I have posted on here so hope I have done it correctly!!

I have a WRX sti type UK (PPP version) on a 53 plate with 144K miles. Full Subaru history with a total strip down and rebuild done by main dealer at 126K.
Also clutch changed at same time. All this done by previous owner so a well looked after car.
After looking on here through various threads I have come to the conclusion that my central diff may have gone as I am getting bad clunking noises from front (both sides) when car very hot. This happens when moving slowly into parking spaces etc. Just had MOT done and passed with no advisories so I know it is not CV joints etc. When car is cold it drives completely normal.
I need a bit of advice please.
Contacted 2 Subaru specialists and one said that the part only is £2700 and that's without fitting!!!
The other one said its £1600 to supply and fit as the gearbox needs to come out? £600 for parts and £1000 labour.
Does this sound reasonable?
Any help would be much appreciated.Thanks