Reti 2.c4 d4 3.b4 f6 4.e3 e5 5.c5-TWIC 898

TWIC 898
The position is already a sharp and topical after
1.Nf3 d5 2.c4 d4 3.b4 f6 4.e3 e5 5.c5 a5 6.Bb5+ c6 7.Bc4 Ne7(diagram) and is analyzed deeply by Delchev in The Modern Reti(Chess Stars 2012).

I don't find the sharp 5.c5 method very convincing because black can play sharply with 5...a5! and now the c-pawn is undermined. White is forced to play sharply just to maintain the equilibrium while black has a number of playable alternatives of which 7...Ne7 is just one.

7...Ne7

Here is the feature game(also game #3 in The Modern Reti).

Berczes,D (2560) - Prusikin,M (2545) 
Reti 2.c4 d4 3.b4 f6 4.e3 e5 5.c5[A09]

TCh-AUT 1st Bundesliga 2012 Baden AUT (3.2), 22.01.2012

Position 1

White has nebulous looking compensation for the pawn invested but the lead in development is significant. What do you recommend for white?

White to Play

18...Kc7