Bowflex isn't the only option when it comes to adjustable dumbbell sets. PowerBlock is another trusted brand that offers its own version, and right now it's on sale. Woot has the PowerBlock EXP Stage 1 (5 to 50lb) adjustable dumbbell set for only $199.99. Amazon Prime members get free shipping (otherwise play $6 flat rate shipping). That's 50% cheaper than a comparable set of Bowflex SelectTech dumbbells and would make an excellent gift idea for any dad who wants to bulk up.
It gets even better. If you need even more weights than the base 100 pounds (50lbs per dumbbell), then you can pick up the expansion kits on sale as well. Both the Stage 2 (50 to 70lb) Expansion Kit and Stage 3 (70 to 90lb) Expansion Kit are only $89.99 each, normally $179.
PowerBlock EXP Stage 1 (5 to 50lb) Adjustable Dumbbells for $199.99
Free weights are a good choice for someone who wants to get as many different workouts as possible in the smallest amount of space and the least amount of equipment. A pair of dumbbells alone grants you access to a wide range of exercises that can target just about every muscle in your upper and lower body.
Each PowerBlock 50 dumbbell is adjustable from 10 pounds all the way to 50 pounds in 5 pound increments with just a turn of a dial. It's definitely more efficient than constantly swapping discs. In terms of space saving prowess, adjustable dumbbells are unmatched. All the plates are neatly contained and doesn't take up much space. You're basically housing two larger profile dumbbells instead of an entire rack of weights.
If you're worried about the quality of these dumbbels, don't. I've tried these myself and they are every bit as solid and well built as the Bowflex variants. The handles are rubber coated so your grip won't slip and the weight adjusting mechanism is smooth and intuitive. PowerBlock backs these dumbbells with a 5 year warranty. If you can still maintain your workout regimen after that amount of time, kudos to you.