Help me decide a type of solo sound for this song, please:

[Axis1~SL61]

It seems I always find it difficult to choose the right solo sound, especially when the song is already finished (except for the solo) and I'm satisfied with it, I often become afraid of ruining it all with an inappropriate solo sound:
http://dl.dropbox.com/u/9415384/2012/24 ... BCatro.mp3
So, what do you think would work best for the solo -- a string, piano, distorted guitar, synth pad, or whatever type of sound?... or maybe even 2 different sounds alternating in different sections of the song?

[If you wanna give it a try before you answer (but that's not necessary), it is in the C major scale , the verse is C all along and the refrain is: e,C,a,C (upper case=Major, lower case=minor)]
Thanks!

[folderol]

A bit difficult to comment really as there is no clue as to what sort of lead line you want! Melodic? Dissonant?

'twer it me, I'd be thinking of a slow, simple, wandering square pad with lots of reverb to contrast with, and sit behind the busy backing.

[fateamenabletochange]

Something distorted, to contrast with the synth arpy bit there already, and the cleaner background chords...guitar ? or Imposcar type big rough sound.?

[Axis1~SL61]

Thanks, folderol and fateamenabletc...
I've tried folderol's square pad suggestion and it works nice. As for the second suggestion I've also tried that and it worked ok too. So, maybe I'll try to strategically alternate these too sounds. I will post the result here later.
Thanks again for both suggestions, it was very helpful.