Some ideas that may help, I myself have a Lonestar Winch on my 5.1 Quintrex which works great and cheaper than the others, but depends on what your excactly after as the Stress Free maybe more suited to your needs.

http://www.lonestarmarine.net.au/

http://www.mickswinch.com.au/

http://www.stressfreemarine.com.au/

Depends on what type of winch?

most of them will take rope and chain so it doesnt need to change from what you currently have ( your minimum should probably be around 6m of chain). The winch just makes it a whole lot easier to pull up more chain if you want more.

size of chain will depend on what size of winch you put on and again, going by the size of your boat 6-8mm short link chain should be fine for a winch like the lewmar profish (has the freefall option which is pretty good).

cheers

brett

I know someone who had an anchor winch fitted on his 5.9m Seafarer.

A lewmar winch was fitted, some mods had to be done to the lid to secure it into place

You could give Neville at Redfin Marine a call, he is very up front with price and what has to be done

http://redfinmarine.com/

Cheers

Had a maxwell winch fitted to the boat at purchase.  It has 10 metres of chain followed by lots of rope (50 odd metres I think).  After pulling in anchors by hand and watching the missus drop it on her finger one day, the winch was an easy sell.  Couldn't convince her to pull it again after that!!!

If I got another one I would be looking for something that can free fall the anchor, the maxwell feeds it out at a fairly ordinary pace.

As a tip, find someway of marking the chain/rope.  Pulling the anchor in a swell can see it swinging around a fair bit and by having a "two metre to go" mark on the chain I always feather it up that last bit and have never had any undesirable contact.  I also marked the rope every 5 metres so I have a good idea what length I have out.  I used plastidip spray paint to mark everything which has been pretty resilient.

Boat is a 632 Signature.

Drum winches have a fixed amount, depending on the size of the drum.
Capstan winches would depend on the size of the chain (rope) locker. Bearing in mind you must have 300mm of chain freely suspended under the winch for it to work well. So what ever length of chain you can pile up in the chain locker and still have 300mm of height between the top of the chain/rope pile and the exit of the chain gypsy.
Bit more info required, pictures as well.

 I have a lone star drum winch and is the best thing I have ever bought for my boat. I have 8 metres of chain and about 75m of rope on top of that. 

Definately get one with freefall option.... 

You might not think you need it and want to save a few bucks, but give it a few trips out with a decent current and wind blowing, you will be kicking yourself you didnt spend the extra!!