I have lousy power - doesn't go out that often, but subject to fluctuations - and two UPSs on 24/7 for two different systems, as well as a Tripp Lite voltage conditioner for laser printer and some peripherals. A Google search for AVR (Automatic Voltage Regulator) or voltage conditioner  should come up with plenty of options.

The less expensive UPS boxes are standby and kick in when the power goes below a threshold, but don't do anything to condition the power quality and just pass voltage variations through to the devices plugged into them. That's not usually a problem for modern PC power supplies, but it can be for some devices.

In my case, one UPS is an APC 650VA box and the other a Best Power line-interactive UPS. They both have worked well for about 15 years, although the batteries need replacement every 5 years or so. For dirty power the Best unit is better because it puts out a clean constant voltage and also provides diagnostics on the input line quality. Best Power was bought by Eaton a few years ago and incorporated into the Eaton Powerware line, which is available in localized versions in many countries.

Word processors and most text editors today work on a stream buffer principle - a single stream of text is interpreted and reformatted into lines on-screen. But there is another approach with roots in the IBM mainframe world: line-oriented editors in which each line of text is a separate record in a linked list. Line-oriented editors have certain limitations which make them unsuitable for some purposes (e.g., searching for multiline patterns) but they have many other benefits.

The best line-oriented editor for PCs is probably Kedit for Windows, an emulation of IBM's XEDIT mainframe editing environment. It's not likely to be anyone's only editor, but it provides capabilities unmatched by any other that I know of. One thing that I love about KfW is the selective editing: You can specify a target pattern and view only those lines that contain that pattern; you can then edit them as a block or toggle back and forth instantly between full and restricted views. You can also restrict edits to within vertical columns or inside rectangular blocks, overlay and fill blocks, etc.  Persistent blocks are independent of selected text so you can use both at the same time. KfWt operates entirely in RAM and is exceptionally fast.

KfW has all the capabilities asked for by the OP, although for the ability to use filters as external user tools, you would have to learn to use REXX, which is probably the least intuitive scripting language ever devised.

The Mansfield Software Group, which publishes Kedit, had planned to cease operations last year, but there apparently is still enough demand for it that they have decided to continue selling and supporting it through 2009.  KfW costs $129. You can get a demo version from their web site which is fully functional but will only save the first 75 lines of a file.