I have an 870 with the surefire forend and am looking to upgrade it. I got it used, but I'm pretty sure its a 618 FA, it has the pressure pad and an on/off switch. It's led right now but it's not very bright, even with new batteries. What are my options for this model? Everything I've looked up has the FA being a non-led bulb so I'm wondering if someone who owned this before me already upgraded or something. Thanks.

You can try a Malkoff Device for about $60.  I have heard a lot of  good things about them but have no personal experience.   I just bought a $15 led from China.  I had to do a lot of modification on my Surefire body to get it to fit.  I like it so far but haven't used it enough to endorse it.

When I had one, I upgraded my 618LF with a Malkoff M60. Made a big difference.

+1 for Malkoff!!