Regarding the KC strings extension, I have one installed on my bass. They're very inexpensive (mine cost about $400 and the install was $200), relatively speaking, and they do the job of giving you a low C, but I've had a slew of issues with the thing that slowly are driving me mad. The Eb gate bumps into the E gate, so I had to have it cut down, the E gate gets loose constantly, and the leather pads on the gates are glued on rather shoddily. Also, since it avoid drilling through the scroll (a definite plus, at least there), the E string becomes extremely difficult to tune, forcing you to check the note, open the gates, adjust, tug the string, close the gate, check the note, see if you're close, repeat. I mean, I'm glad I got the extension, it's made a lot of orchestra parts possible in the way they were intended by the composer, but there definitely is a trade-off with the price. The tuning problem can be mitigated with a fine tuner on the bridge (something which I am very seriously considering purchasing.) and there is the upside since that KC strings extensions dont damage the scroll in any noticable way, you can always remove it or trade it for another, better extension without any real problems. All the local guys around here that do good extension jobs, however, have huge waitlists and cost several grand. So. Yeah. If you're going to purchase a pre-made KC strings extension, it will save you a lot of money and trouble, but I'd suggest getting one with just an E gate and leave the others off.
