the pads and kontrol are excellent...the keyboard is shit...its not real keys but more like buttons...this is a far better idea and has an excellent arpeggiator, tap tempo, and a sustain button...
all of them will work with Abelton Live....if it doesnt have an assigned map you just activate them as usb controllers in the preference page and assign the midi controls out to wherever you want...you can even use the pads to activate scenes and mix/record them in real time...
this sketch was recorded just using the lpk25, a netbook, and Live whilst on vacation....drums were programmed with it too
Even if you don't play keyboard, there's some reasons to buy one. For one they sold tons of them so you'll see them pretty cheap used.
And with a keyboard like my Evolution MK-461C, as well as 9 faders and 12 rotary pots you can assign all the piano keys to MIDI commands. So with the wheels and pedal input it's got 85 assignable MIDI control message capability. So even a short version 49 key version would be good too.
What I usually do is buy used and not really "have to have a certain model" but try to get a great deal from what's out there. I've seen good controllers for $20.
But any of those you were looking at looked good too.
I always prefer Craigslist, as you get to see and try it plus avoid shipping. Of course eBay's fine and I've bought new from www.audiosyncrazy.com If you check around and phone them they'll usually beat anybody.
I've had trouble with Musician's Fiend and have had good results from Zzounds.
I bought my lpk25 from a company called "hip hop tools" on ebay...it came with a huge collection of individual hip hop drums from sample cds that they sell...excellent value