I find when you're young the Ibby necks are great & allow a lot of flexibility, but I'm finding the slim neck uncomfortable for holding chords or octaves (or anything that requires a little pressure). This is due to me getting old tho & can't fault anything else about my SR1000. The pick ups say USA C1 on them and I haven't a scooby what they are, but I like the sound & other than getting a thicker neck on it, I can't think of any upgrades that I'd do. Maybe a Hipshot?
I've had mine for nearly 20 years & the only thing I change on it is the strings. Although I've thought about a few things & then thought, Naah.