I'm very poor and extremely young but I have an esp ltd d-5 tuned E0 A0 E1 A1 D2 G2 with a .165 conklin sit for the low E. This is lasting me until I can build my 38 inch 6'er to add an A00 under the E0 and also to tune it up(tune it up? haha) to C0 F0 C1 F1 etc.. for my other band. I know what your thinking but the A00 isn't as much for musical notes as it is for 'percussive rumbly earth moving abience'
tm (made that up

). the C0 for my other band is used as an extension of the low F0 so I can go down and up. for example If I have a riff where I hit a 6 on the f string and then a 1 on the f string I can just pop down to the c0 string and be extremely fast in the low sector. I am using this to great effect to play metal on the a0 string when I can just go down to the E0 string. Okay I'm done ranting

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EDIT: A word about the sit power steel, its a really really good string but I hate the contact core. It adds these hollow overtones on any fret above 11 or 12 and its annoying. I'm going to order custom strings from gary goodman next time and get a non tapered string. Also If anyone is wondering I play a baritone guitar tuned to Drop f, So I dont have to deal with guitarists crying about my low range.