Need A/V reciever for HT 5.1 or 7.1; Have 4 ohm Polk LSI

I am upgrading my HT system. I had a cheap HTIB. I have acquired Polk LSI 7 speakers total. LSI center, LSI15 fronts, 4 LSI FX surround (2 will stay in the box). All the speakers are require 20-200 watts with the fronts capable of 250. When I move in 2 years I plan on having a larger room capable of 7.1 I need a AV receiver that will work for these 4 ohm speakers. I have a cheap sony 100W/channel at 8 ohms. From the info that I've gathered I'm afraid to use it even temporarily and risk ruining the amp or speakers. I was hoping for Input on a good Reciever that's either 5.1 or 7.1 that will not have any trouble driving these speakers. I'd prefer to spend little as possible with $1600 being the limit. Names that I've been told to consider are NAD, Marantz, Arcam, Rotel, Harman Kardon. I haven't been able to tell definitively which ones can handle the high current. Any input on this topic would be appreciated. Thanks.

I also need a subwoofer I can get a velodyne CHT12 or Polk 12" PSW505 for cheap, but I was told that neither of these are good enough for my set up. Any thoughts?

Could go with a receiver with preouts, such as the Marantz SR-5400 for $550 delivered and a couple of Crown CE1000s for $450 each delivered or an Outlaw 7100 for $946 delivered.