Hi. My budget is about 90$ tops, and I'm not sure if I should buy the Ultimate Ears 600, or the UE500 with a Fiio E5 amplifier.
Which option is best for Rock music, to be played with the SanDisk Sansa, Zune or HTC Desire?
Neither, if you like the UE sound (which I do) go for an older pair of SuperFi 5 Pros or Triple-Fi10s. Both sound better than the newer (Logitech) UEs and BOTH HAVE REPLACEABLE CABLES, which is a big deal if you plan to own these beyond the warrantee period as UE cables only last about 6 months max of regular use for me.
No, it's a bit confusing because UE did make a Super-Fi 5 and 5vi that has since been renamed the UE600. I had a pair of those and they are decent sounding, but lacking in build quality and durability.
I am suggesting the Super-Fi 5Pro or the Triple-Fi 10 (aka TF10, TF10Pro, TF10vi), which are older than the Super-Fi 5 and Super-Fi 5vi, have the replaceable cables, and better sounding (especially the TF10).
And $130 is a very god price for the TF10, probably average for the SuperFi 5Pro, which are getting hard to find. Check the FSoT forum here. You are better off spending $100-$150 on these than $75-$100 on the UE-600 or Super-Fi 5.