If the approach requires a DME arc or DME distance fixes and does not have an
approved GPS or GPS/ARNAV (advanced area navigation, to be required at the
upper FL's in 2005), you're stuck.  The FAA has started creating GPS based
equivalent approaches to substitute for all approaches in (supposedly) the
following priority:

1. NDB
2. VOR
3. VOR/DME
4. ILS (this will require WAAS and may still only be good for Cat 1)

IOW, if you typically fly where they clear you to a DME approach and they
don't list a GPS equivalent, you need a DME.

If you have the panel space, a used KNS-80 can be had for ~$1000.  Yes, the
RNAV is pretty useless by today's standards, but that's a cheap price for a
DME/VOR/LOC/GS.

Eric Ahlstrom