for dumbells, i strongly urge you to get the no-fuss, no-frills hex rubber dumbells, cheap, easy to maneuver, durable/resistant to throwing/dropping on floor, not painful to put on your lap/quads.

i've used those plate-adjustable with nut to screw-in type, used bowflex, and used those round urethane(EXPENSIVE just because it's "smaller" for any given weight) dumbells, and none compare to a basic hex rubber dumbell.