I think that would depend on listening levels. For low to moderate listening levels you don't need anything fancy for movie surround effects. If you like it loud (movie theatre levels) then a more dynamic speaker is going to be able handle the big effects better. If you also enjoy surround music, then it can make sense to put a little more into surround speakers.
I have also read good things about the NHT SuperZeros for those on a budget. You could try one pair and maybe even swap them with the RC1s to see how they work as side surrounds. If you like them you could replace the RC1 with another pair. The used market is a little more of a chore but if you state what area you are in, members might be able to recommend something on Craigslist or USAudioMart. Crutchfield.com also has the Kanto Yu Passive and the JBL Stage A120 discounted right now. The JBL A120 is normally $250 so at $150 is a very good value.
I would also consider saving up for a better subwoofer. Many that are new to the hobby underestimate the impact of a good subwoofer. The little ASM-8 probably doesn't do much below 35Hz and a true subwoofer should have usable output down to 20Hz. If you can't fit a 12" sub in the room, there are some decent 10" subs available.
Erin's Audio Corner did a round up of some budget 10" subs here. Dayton and Monolith also have some good budget options.