I recently installed a channel modulator, and because of the layout, I needed a 3-way splitter. Here's the layout:

http://img524.imageshack.us/img524/4831/img0152ib7.jpg

Bottom of that splitter comes from the wall/street. That bulky thing on the right is a low pass filter that blocks the channels where I'm inserting my own. The middle connection goes to a dual tuner TiVo. The leftmost connector has no signal. It would be going to my non-HD Comcast box. Instead, I've connected the cable box to "Local" on my Sony MRD-D1 modulator.

http://img261.imageshack.us/img261/7189/img0156rs3.jpg

This modulator ain't the best, but it's cheap and does what I need. I only need these channels on 1 TV; it's about a 40 foot run. The picture ain't perfect, but good enough.

Since I do want the cable box to get a good picture, I don't want to have it get its signal out of the modulator. So maybe I need to amplify the signal before it goes into the 3 way? I already have an amp (on the side of the house) between the street and my first splitter; but I don't know the specs because a painter decided to paint over it.

Will performance suffer if I double amp? What about an unbalanced splitter?

Use a better splitter, one with a wider frequency range.

Yeah, I'd definitely say get a 1000MHz splitter and eliminate that part of the chain before trying amps and such.

I thought that signals for standard or "digital" cable didn't go that high...?