I looked at Bowflex Selectech, Stamina Versabell, Ironmaster Quicklock and Powerblocks.
: I had the chance to see these in a store. I wasn't impressed. $399 for 52lbs is alot, but what is worse was that the thing had problems catching on to the weights I dial in. In most cases, turning the knob, selecting a weight resulted in me picking up only the handles. Possibly the display model was broken, but that does not bode well for durability. Honestly, it just looked like a poor design to me.
: I liked these better then the Bowflex junk, but that is not saying much. Once again it is limited to 50lbs with no ability to increase in weight, but at least it only cost $279. I think they only increment in 10lbs, so that is not so good. It's a solid design, but leaves alot to be desired.
: These are pretty decent. 5-75lbs for $429 with the ability to increase to 120lbs for an additional $179. They are basically a spindal handle, but it locks into the handle so the handle is never any longer then the plates. It's durable looking and pretty much same as buying a dumbbell handle with a star lock and plates, but more clean design. Changing weights requires you to unscrew each lock, put on whatever weight plate you need to get to the weight you want and screw the locks back on. You'll still have weight plates to contend with as well. I like it, but I like powerblocks more.
: 5-50lbs elite for $349 (cheaper then bowflex, much better design and can be upgraded to higher weights), can increase in weight to 130lbs. I opted for the 5-90lbs set for $549. I read many many reviews about these, nearly all of them were good. Weights are changed simply by pulling a locking pin. Many people have owned these for years and reported they are very durable.
For a dumbbell bench, I went with with the decline crunch, dip bar and chin-up attachments. Very space saving and sturdy looking design. Although I haven't seen this bench in person, I am very impressed with what I have read and its adaptabilty, hopefully it lives up to my expectations.
For limited space, this is a very good set-up I think. Dumbbells can provide all the workout equipment you need. A full blown cage system might be better, but not everyone has the space or are inclined to let their home gym take over their home. I have tried Bowflex resistent rod and similar benchs and I really didn't like them. Besides not liking how they feel, they also took up quit a bit of space and were an ungainly sight to behold.
These dumbbells along with a bench that allows me to do dips and pull-ups are pretty much all I need in a very compact set-up.