There isn't a drastic difference in reliability between the HTF600/HARX700 stuff and the higher end stuff. They're all manufactured from the same plastic in the same factories in Taiwan or China until you get into the $200-300+ range where things begin to be more "boutique" and may be made in Germany or have wood/metal components.
Basically, you pay for improvements in detail, speed, clarity, balance, etc. If you want mp3s with the bass turned up with no amp straight from a phone then most of those improvements won't even be audible. In some cases (AKG, Beyerdynamic, etc.) the more expensive headphones will actually sound far worse because they're so starved for power.
If you do decide to go with a quality amp and by "bass heavy" just mean a bit of scooped sound signature, then yeah, spend as much as you can afford, because then you can hear the improvements. From what you describe though save some money and go with Panasonic or JVC.
Edited by machoboy - 9/8/12 at 5:02pm