advice for a sander & polisher

I am looking at building a pair of speakers and finishing with a black satin painted front and a wood veneered sides on mdf and seeking some advice on what sort of sander to get. My thoughts are to get a sander that can do both the preparatory rough to fine sanding and finish of polishing the finished painted and varnished surface.

But there are a myriad of sanders out there!

Just looking at the Makitas there are
http://www.justtools.com.au/images/bo5021kx1_sml.jpg Makita 125mm Random Orbital Sander. #BO5021KX1
which seems a good choice but also

http://www.justtools.com.au/images/bo3700sp_sml.gif Makita Finishing Sander. #BO3700SP

and also
http://www.justtools.com.au/images/9207spb_sml.jpg Makita 180mm (7 ) Sander - Polisher. #9207SPB
which also seems really good.

Not hung up on any brand just using these links/pics as demos of the very different types that are available.

Any recommendations to type of sander/polisher would be greatly appreciated!

I have just gone down this track myself and settled on the ROS BO5021KX1. I'm like others very happy with it and surprised how nice it sands. I found Trade Tools Direct the best price in the end.:D:D

SB