Bicycle Mechanics - xram derailleur system explanation?

Hi, folks:
I'm pretty ignorant about current offerings in derailleur systems, but a couple years ago I bought a cheap REI bike that came with an xram 3.0 rear derailleur, and grip shifters. I've absolutely loved it; found it rapid and completely reliable with my wide-range gearing. I ride on pavement and don't bash it against anything. Perhaps that's why I've found it so satisfactory.
They don't offer that one any more, and I'm building up an old frame and want to have grip shifters. They now offer X.4, X.5, and so on. The satisfactory performance of the 3.0 I have leaves me to suspect I'd be happy with the cheap x.4, but I don't know what grip shifter would work with it. They've introduced terms like "compatible with ES systems", or "1:1 ratio". I know enough to realize I've got to get the appropriate number of speeds on the shifter (probably 8), but am worried about getting a mismatch in terms of compatibility. If I bought an x.4 or x.5, can I make a mistake in choosing the shifters? Any great advantage in the more expensive ones, in view of the gentle treatment they'll get from me?
Thanks much,
Chas.

Fiction!

I think you mean a SRAM.

They still make the 3.0 shifters if you need a 7 or 8 speed setup and of course you can get several different 9spd grip shifters.

http://www.sram.com/sram/mountain/category/6

Try clicking on some of those shifters and looking at the "Specifications" for how many speeds each will work with. One of them even works with 7, 8, AND 9 speed systems. The main thing is to make sure the derailleurs you get have the same pull ratio as the shifters you get.

Fiction!

I think you mean a SRAM.

They still make the 3.0 shifters if you need a 7 or 8 speed setup and of course you can get several different 9spd grip shifters.

http://www.sram.com/sram/mountain/category/6

Try clicking on some of those shifters and looking at the "Specifications" for how many speeds each will work with. One of them even works with 7, 8, AND 9 speed systems. The main thing is to make sure the derailleurs you get have the same pull ratio as the shifters you get.

Ok, thanks. Followed your link and found a 3.0 shifter. It's my rear derailleur that says
"3.0" (and nothing else). The 3.0 shifter on the site shows 3 speeds; my shifter shows the 8 speeds I have on my cogset, and looks different from the shifter on the site.

the 3 speed one in the picture is the left/front shifter. This is why I said to click the specifications on each shifter to read the details:

Speeds Rear: 8/7 Index, Front: 3 Index, Micro-index
Compatibility SRAM 1:1 rear derailleurs, SRAM front derailleurs, Shimano® front derailleurs

SRAM grip and trigger shifters that have a number (or 0) in the name will work with SRAM rear derailleurs. If it has a name, like Attack, it will only work with Shimano RDs.
You do indeed need to make sure that the specs for the shifter you are looking at say 8-spd for the rear. The front shifters will all work with 3 speed cranks. (or with double cranks).
Any of the SRAM numbered shifters will work with any of the numbered RDs, as long as you pick an 8-spd shifter to match your 8-spd cassette.

Okay, this was all most helpful. thanks and pardon my being so dense. I think I'm dialed in now.