q1000 is a technically a vdsl2/adsl2 modem while pk5000z is just an adsl2 modem, so depending on the technology serving you, would determine which modem you could use.
qwest has just replace my modem with the pk5000z & told me at the time they do have a better & faster internet avalible in my area but they want $5 per month to lease the modem,
