where does everybody buy replacement mufflers for pathfineder?
midas or meineke any preference?

You might want to consider a custom muffler shop. You might be pleasantly surprised - I had my '88 Pathfinder's exhaust done in stainless steel a few years back for about $600. Midas on the other hand quoted me close to $1000 for regular steel.

had the middle muffler replaced by meineke last week for $328.31 total.
that's after a 25% off coupon i found on their website.