hubcentric would be better but not essential. longer bolts would be essential though. you'll definetely get them on the front, but with the exception of looks i doubt theres any gains to be had in terms of handling but i would love to be proved wrong.
hubcentric just relieves the stress from movement on the hub, but its only 10mm. so unless its going to be a permanent decision i wouldnt bother. just go for the cheapies and then take the decision from there. but you can get eibach pro spacers cheaper than 40quid, and bolts are circa £2 each.