Just get the RRA, you'll be very pleased. I highly recommend midlenth systems and RRA's is about the best you'll snag for a factory weapon. putting a block in place of the FSP is common and easy to do yourself. Get a railed gas block so if you chose, you can put a front flip up on it.
Like about 89% of what you read on the net, take ARFCOM with a grain of salt - my ramblings being in the other 11% of course
, It's more about divesting the worthy information from the raw crap.. good luck, there is a ton of crap on ARFCOM.
Talk to a shop that deals with AR's.. Jensons in Ft. Collins CO is a good one, a couple of vendors on ARFCOM are guys I would and do trust.. Leagle Transferes and Paul from Bravocompany (www.bravocompanyusa.com)
. And please take your time researching your gear.. there is a ton of cheap arsed stuff that will and I mean WILL break on you when you need it, buy once cry once when you buy AR stuff.
What I really want to know is why you think the front sight post on the AR is something that should be pulled off - seriously interested in why folks make certain mods to the AR platform - ? More over, am I understanding that you do not want Iron Sights of some sort on the weapon? Even for matches, better to have back ups, either extra glass or mounted backups - check out the Troy flip up sights - Hell I'm a huge fan of co-witnessing and like the red dots for that reason (read AimPoints and EOTech) but I would never run an AR or any long sight radius weapon without BUIS because Murphy goes shooting too
If you want to read some solid info on some of this, take that same 8 hours and more, go to www.lightfighter.net
and be ready to learn.
As for the gas block.. +1 for what was said earlier, but note that you will also need to remove the flash hide/supressor in order to slide the FSP off of the barrel.. talking to one of the two folks I recommended with clairify that more.
Hope that helps..