I will say, that firstly...why buy a £500 new gun, for £500, when you can buy a £900, second hand (just, usually) gun, for £400?
Of course it's up to you, but the secondhand forums are an excellent place to visit if you have cash.
I will always say Ego, over a Shocker...but...over an Etek...dunno..I like Shockers.
Egos and Eteks, are way easier to tech than shockers, and are less likely to go wrong, simply because of teh fewer parts/o-rings etc.
If I were you...I would take my £500 to the classifides and buy a nice Ego...maybe an 06.
Or, a DM5 or 6 maybe...better than a shocker, by..well a long way.
Similar bolt design, so o-ring maintainance is a must...very cool gun tho..I love em!!