My thoughts:
1) I like how clean the XP bar looks right now, IMO it doesn't need two different numbers.
2) BUT....... if you are going to make a suggestion like yours, I would just have 1 single number counting down. So if it takes 3000 XP to get to the next level, it starts with "-3000" and if you donate 5 archers it becomes "-2995" until it finally reaches zero, that's when you level up. You don't need two separate numbers, you know what I mean?
3) I prefer to just use this site to tell me how much XP is needed before I level up:
http://clashofclans.wikia.com/wiki/Experience