Which of these amps for Kef Q300?

Hi there,

I recently bought Kef Q300 which are currently connected to Onkyo A-5VL digital amp. Results I'm getting are far from satisfying, and nowhere near as good as with NAD 356 I auditioned the speakers with.

I have a change to exchange my Onkyo amp for one of the following slightly used, but in perfect condition amps:

Denon PMA-710AE

Cambridge Audio 350A

Marantz PM5004

Yamaha A-S700 (one and a half year old, not in perfect condition, visually damaged)

What I'm looking for is a detailed, clean sound, with well defined mids and vocals, and tight controlled well extended bass.

I'm not getting any of that with the Onkyo, its a sort of harsh sounding amp, with pulled back and lifeless mids, not very detailed highs and weak, poorly controlled bass.

What are your suggestions? Feel free to suggest other amps at the price range of the ones I've mentioned above, but remember than I would strongly prefer one of the above.

Also, I'm currently using the cheapest Cambridge Audio cable, those bronze ones with pink plastic wrap around them. Is that sufficient for the Q300's or should I opt for something more expensive?

Thanks