4 ohms or not, for those kind of speakers I wouldn't bother with separate amps. It is not uncommon to find those tiny HTIB speakers having 4 ohms or lower impedance, yet no one worry about driving them with power amps. I think most people simply stick with the stock OEM receivers/amps or whatever gear that are part of the package/box.
Back to the OP's speakers, they claim 150W power handling capability but they probably mean "music watts" or something like that but please don't ask me what music watts are. If anyone wants to know may be ask Sony, Sanyo, Samsung etc. I am pretty sure if you power those things with a real 200W amp you will blow them up quickly if you are not careful. And please don't tell me it is under power that blows speakers as you know that I know the drill but.............
For $500, you can pick up a Yamaha RX-V863 and then add separate power amps when you are ready to upgrade your speakers.