I use a Kaiser VP6005 for colour work. It is a very sturdy enlarger which uses a combined condenser/diffuser system. Light is passed through a double condenser and then through a diffuser. I find it very easy to use and with the right lens gives excellent results. My own enlarger will do up to 6x6. The Kaiser is a modular enlarging system that allows you to tailor the enlarger to suite your needs. You can buy the necessary condesers and the same enlarger will do up to 6x9. Other items available are long columns to allow prints up to 20x16, VC heads if you are only doing monochrome.
If you are on a budget you could also do a lot worse than the Meopta Magnafax. This enlarger will do up to 6x9 and, again, there are a lot of easily obtainable accessories for it. It is an all metal enlarger that is very substantially built. The negative carrier is superbly made. I used a Meopta Opemus 6 for a long time and was very satisfied with it.