I used to deal with Deanta in a previous life. Their doors are generally of a good quality and they have some nice designs. Their stuff is all pre-finished (or used to be anyway) so you can just hang them without worrying about paint or varnish, and pre-glazed so although you might find choice limited, they are simpler to sort out. Their matching joinery is nice too.
However, I always found them a bit hit and miss with regards delivery. As I understand it all their gear is brought in from China. Now I didn't have a problem with this as it's all well packed etc, but if they don't have in stock the sizes / designs that you want be prepared to wait. Also, and this may well have changed, they didn't always send out what was ordered and a few times I had to send things back and re-order.
I also used to deal with Doras. Generally good stuff (bit better than deanta at the top end but comparable quality and price in the mid range and cheaper at the bottom end). They were always pretty reliable too.