I've been through a few budget headphones. I'm really enjoying my latest buy, the Audio-Technica ATH-T400. They are a closed phone and provide really good isolation and are pretty comfortable. Other budget phones I have are the HA-RX700 (slightly less expensive sister of HA-RX900), HD205, and the JVC HA-S160 and a hodgepodge of various cheapies. I prefer the ATH-T400 to all of them. HD205 has good extension and good detail, but highs are harsh and the overall sound is slighlty tinny. The RX700 have a bit too much mid-bass bloat and vocals are not the best, taking on a slight nasal quality. (Even after modding) Once they are burned in, the ATH-T400 has more detail than the RX700 and provide a fuller sound than the HD205. Mids are a lot better than on either the RX700 or HD205. Treble is a little weak, but they respond really well to EQ so its easily compensated for. They are a good introduction to the A-T house sound, but with that said, the A-T sound is not for everyone.
They provide good sounstage for a closed headphone, but they are nowhere near that of most open phones. If one of your goals is a to have a lot more space and sounstage, you may want to look at the open and semi-open phones. The aforementioned superlux are often recommended but I have not heard them myself. Grado sr60 are also in your range. They are very open, leak a whole bunch of sound, have an awesome soundstage, and are quite bright. Again, the Grado sound is not for everyone, but they are worth taking a look at and you may discover that that is the sound you are looking for.
Edited by Ubersanger - 1/20/12 at 2:40pm