Racket Rrp

Which Tennis Racket for my 10 year old son?

I'm looking for a tennis racket for my 10 year old son. He's been playing for over a year now and is taking it quite seriously so I am happy to pay up to £60 or £70 if that is what is needed to get a decent racket. He is 147cm tall. I have been advised that he could now move up to a full size (27") racket. I have looked on pwp.com and see that they have some discounted rackets including:

Wilson Hyper Hammer 4.0 (260g, 27.5", head 113 sq in) for £70 (RRP £150)
Wilson Hyper Hammer 5.3 (270g, 27.5", head 95 sq in) for £70 (RRP £180)
Head Microgel Radical (280g, 27", head 102 sq in) with bag for £80 (RRP £120)

Then someone else offered to get me the latest technology in a Wilson K Bold BLX (262g, 27", head 100 sq in) for £65 (RRP £80)

Can anyone advise me on which is the best buy??

Thanks.

None of the "latest stuff" technology matters if the racquet does not "feel good" to the player and fits the players swing. The best thing to do is go to a store you trust, that has people who know what they are talking about and "demo" the one's he is interested in that fit your price range. Even better would be a shop that lets you take the racquet out to a court and play a little with it ( think test driving a car).