556uw v dlpk

I'm looking to have installed on my 09 Mitsubishi Outlander a Viper 5901 system. However, the Viper website says that I need a DLPK but the Directed Electronics website and teh guy at best buy say I need the 556uw. My vehicle has the FASTkey system. What is the difference between the two? Do they both do the same thing? TIA

Viper 5901 on a 2009 Mitsubishi Outlander

xpresskits is just giving that as an option for doorlocks, factory alarm arm/disarm, hatch release, door triggers.  It won't bypass the chipped key.  That is why best buy suggested the 556u

dlpk will do the transponder if you get the RFLMIT3 RFloop for it as long as it not a Canadian originally import vehicle you should not need a dealer scan tool

So does that mean if I don't get the DLPK, then the remote won't unlock/lock the doors or release the hatch? Am I correct in assuming that I'll have to burn a key to get this to work with the 556UW? Monty - are you saying that if I get the RFLMIT3 with the DLPK, then I won't need the 556UW - it will do the bypassing? Will I need to burn a key with this combo? Thanks for the help guys, obviously I'm a n00b here, but it's starting to make a bit more sense.