What area are you in? I'll see if I can find out when 4G LTE is coming to your area....if so, I'd wait for a price drop or sale for the LG Optimus F7 or HTC SV One.
The 4G for Boost is "par" compared to other 4G networks...the thing is that a lot of people don't experience 4G anymore though because of the new push for 4G LTE on all networks (Pre-paid included).
If I were you, and you're having problems with your Marquee (like most Marquee users), I would spend the $150 on the S2. The LG Optimus F7 isn't going to have a major price drop (or sales) for sometime. It's going to stay $250+ for another 3-4 months still or longer. The S3 is not going down in price any time soon either. You could go with the SV One from HTC, but it just had a price drop and it went to $280.
So overall...I'd say the S2 for $150 is your bset deal for a while.