I like the bottom feed too as you can use the small color cups instead of the bottles if you want, but I have one of each because the bottom feed is only a .5 mm tip. The gravity feed has a .3mm tip. I have always used Dixie as they used to have free shipping over 50 bucks but I do believe they went up on the total for free shipping. If I could only own 1 brush it would be an Iwata BCS as it is a very versatile unit.
http://www.iwata-medea.com/index.php/products/hp_bcs/
I use the Badger color cups as I have found them to be cheaper than Iwata. They fit perfect on the BCS. Not the side feed cup though. 1/4 oz size .
http://www.badgerairbrush.com/Acessories_8.asp
As far as compressors go IMO, for what that is worth, I would get one that has at least a 10 gallon tank. Mine is 15. The reason is I can power it up and then shut it off and can do just about every thing I do in a session. The smaller units will need to cycle more often and I don't want to listen to them. I would also go with an oil one too, longer life. Don't forget to drain the tank after each use to avoid condensation in the tank. I use a water trap too but have never had a drop of water in it. I also like a 50' hose too, most come like that anyway, as it seems to regulate the pressure better. Sears have several nice units and are on sale from time to time. Have fun.
Here is a good site for info
http://www.airheadairbrush.com/