x2 Grados. If you're lucky, you may get the RS2 for around $300. If you prefer the in your face rock, then the top two prestige lines (SR225 and SR325) will fit the need. If however, you prefer something more musical and less bright than the SR325, the Alessandro's is the best replacement. I think your price range is very ideal. I find it all too often, myself included, that starting at the low end will inevitably lead to where you should have started in the first place. I started with the SR60 and moved up to the RS1i all within 6 months! For electrics, you may find the top prestige lines more fun and matching. For acoustics, there is no other choice than the reference series.
Have fun.