As fair warning, this involves rooting your phone, which voids its warranty. BUT I just completed the firmware installation on a refurb'd Marquee and it runs very smoothly now, particularly compared to the frame-droppy mess that it was before (which is sad...the phone has a 1GHz CPU in it so it should run nice and smooth even with stock firmware, but I digress).
Anyway, here's how you root/install ClockworkMod Rcovery (required to flash the ROM):
Note that you need to install msxml as well as the other stuff, otherwise the firmware downgrade won't work (the downgrade is the trickiest part of the whole process). Also, at least for my phone you'll be following the Sprint instructions, even though the branding on the phone case is Boost Mobile.
Now for the easy part: download CTMod to your SD card's root (you need a microSD card for this), reboot into CWM and apply the zip. Your phone will be factory reset in the process.
You'll need to reinstall all your apps, including any Google apps (Voice Search, Maps, GMail, etc.), but that's okay...things run faster that way.
This ROM is still Gingerbread (there are a couple devs working to make ICS/JB a reality) but, for an inexpensive refurb phone like the Marquee, that's perfectly reasonable.