i guess he's talking about SX as a brand in general.

i'm not too sure but i guess they're widely known as a budget line producing strat copies, tele copies and the like.

i'm thinking of getting a cheap tele copy. SX would be something im looking it. and then, i'll change out every single possible hardware to cater to all my standards as a musician.
I have a number of them, SST's (strat Copy) STL (tele copy) SJM (explorer copy). I really like them, some are modded some are stock. IMO for $100 you can't beat the SST or STL. For just a little more at $200 the Agile AL2000 (Les Paul Copy) is hands down the best guitar I have seen at this price.