That's a major "depends" type of a question. The 500.1 will be more efficient for the subs then the 800.2, but on the other hand...while you will have more power for the cabin speakers, you will take another big efficiency hit over the 400.4.
Personally, I say if it ain't broke...don't try and fix it.
Your cabin speakers will benefit from a bit more power, that's for sure, but you need to ask yourself if it's worth $370 for the JL's. IMO, they look a bit nicer, definitely have a great crossover section, and are good amps.
The RF's have a bit more flexibility then the JL's becasue of the RIPS system.
I would also look into the heat factor of those RF amps. The one's I have owned in the past could have worked well at the tail-gate party as bbq's....I'm not sure if that's an issue for you or if the JL swap would run cooler.
As you can see, there really is no way to decide this one...there are benefits to both systems. If anyone tells you one way or another with no real good explanation, then I would say they are a bandwagon jumper. Both are quality setups. I say it comes down to money.
Just my $0.02