Sexiest would be one of those things that are "eye of the beholder" things. Once you get what you need(size, fan capability, drive space, etc) get whatever you think is "sexy". What might be sexy to me (haf 912) may be totally disgusting to you. You are the one that will have to live with it every day, so it should be your choice.
One case that is great for $50 is the Rosewill Challanger. I just built a friends rig with this case and I was very impressed. I was able to fit his AMD 7870 in it with no problems.
Full black interior
Advanced Cooling System :
-Front 1x 120mm Blue LED Fan (pre-installed)
-Rear 1x 120mm Fan (pre-installed)
-Top 1x 120/140mm Fan (140mm pre-installed)
-Side 2x 120mm Fan (Option)
Screw-less design for 5.25" Devices & 3.5" HDDs.
2.5" SSD/HDD adapter allows to install 2x 2.5" SSD/HDD into a 3.5" HDD slot.
Mesh design front panel with dust filters.
Top mounted IO ports– 2x USB, 1x eSATA, Audio out, MIC in.
Advanced Bottom-Mounted PSU Design.
PSU shock-proof pad.
Dust filter for PSU.
Motherboard cut out