Okay, having bought a lot of stuff from OLX, I have begun to understand how it works. What I do is, when I see something exciting, I check 'More ads from the seller'. Individual sellers would have very few ads listed usually in different categories, on the contrary, a dealer would have a lot of ads either in the same city or different cities selling AV equipment only and nothing else.
I see no harm in dealing with a dealer, as long as he is in the same city or another where the product can be physically inspected. If neither fit the equation, move to the next ad, don't even bother about it.
My entire Hometheater gear has been bought off sellers on OLX and so far, touch wood, everything I have bought has been excellent. Plus I have made some friends too. No harm in having a dealer friend, keeps you informed of the stuff.
Currently looking for a Big TV and have come across sellers who sell just off the market equipment in sealed condition, at almost half the MRP at which they were being sold when in market. I mean, yes we lose out on a couple of latest features, but for the average Joe like me, I am happy to get a top of the line product(in its days) at half the price.
All the best.
MaSh