I would like some advise on which which amplifier would best suit my system. am looking for a new amplifier and I like the new Arcam series, I am in doubt whether to choose the A5 or A15. The other components in my set are: Phono: Audio-Technica AT-LP5X; CD: Marantz CD6007; Speakers: KEF Q750. Pricewise the A15 is in a different class, should I therefore choose the A5? Would greatly appreciate your opinions on this.