Yeah, the bands are a great way to cut down time on EV training.
On a side note; I HATE the Crawdaunt with Quick Claw and Guillotine...It almost never misses T_T
I was scared it was going to kill me. xD
I was going through Battle Tower to get the Power Anklet to finish EV training my Elekid and Gligar. Came across this Crawdaunt twice. First time it had two chances to hit, but didn't. Came across it again, and it missed, I felt lucky. But then later on my Sceptile had died, and I had Metagross and Swampert left. He had Meganium and Skarmory. I switched to Metagross. His Meganium Leech Seeded me, then I missed with Meteor Mash, giving it a chance to make a subsitute and slowly get my health down with Leech Seed, and when it was low, it'd just use Synthesis. My Metagross died, but then when I switched to Swampert it used Giga Drain, I Mirror Coated, it died... Skarmory next... it critical hit... -.-' I was so mad. xD
On topic now...
Deathmage129 is right, all of the Power Items only add +4 instead of multiplying it by 4.
Say you're EV training against Machops for +1 Attack EV each time.
If you have the Power Bracer on: 1 Attack EV + 4 Attack EVs = 5
If you have the Macho Brace on: 1 Attack EV * 2 = 2
Macho Brace + PKRS: 1 Attack EV * 2 * 2 = 4
Power Bracer + PKRS: 1 Attack EV + 4 Attack EVs * 2 = 10
Best way to EV train is with the Power Items, it's even greater than Macho Brace + PKRS.