You can get these strings from Amazon… Thomastik Strings for Acoustic Guitar Spectrum Bronze Series nickel free set SB111 light .011-.052
So, I bought the Thomastik-Infeld Spectrum Bronze (.10 – .50) and I’ve put them on my Dean Performer. The sound is absolutely fantastic, and, yes, I do believe these are the best strings for acoustic guitars fitted with a pre-amp (and, of course not fitted with a pre-amp). I’ve still got the sitar sound on the top E though, and, after watching a YouTube vid, I’ve realised that the saddle needs replacing. I bought this guitar for £20 from a local charity shop and I replaced the bridge then with a bone one. It appears to have worn to the point where the sitar sound is annoying. I found out that if you’re getting a sitar sound in open then replace the nut. If the sitar sound is noticable only when playing notes up the fretboard, then, replace the saddle. I’m also looking at replacing the pre-amp, mainly due to the fact that the newer ones have a better piezo pickup than the metal strip one on my guitar. I’m noticing slight differences in volume when different strings are played, and a new pre-amp will probably sort this out. Anyway, I can highly recommend Thomastik-Infeld Spectrum Bronze, although I do think a slightly heavier gauge would be even better.