Speaker selection for a 4x10" cab

[79strat]

I've replied a few times to questions on 4x10" cab dimensions and now that I've started to build one, I've got some questions of my own!

I'm building the 4x10, along with an 18-watt head for a friend's son. He decided to go with the "half-stack" look because of course... it's classic. I'm wondering what speaker to use in it and am somewhat worried about volume (or lack of it... I know that sounds stupid). I want this kid to love the amp and have it last a good long time. Is pushing 4-10" speakers in a closed-back cab too much for a pair of EL84s? If not, what does everyone recommend for speakers - it needs to be relatively inexpensive as well, in the $50-70 range per driver.

I'm assuming the usual suspects - Celestion, Jensen, Eminence, but I have no experience with 10" speakers, just the 12" Celestions in my other cabs.