Graeme
Kodak, evil old Kodak, has published TONS of accurate data for decades
which will tell you what you need to know.
first, go here:
www.kodak.com
then, click "ProPhotographer/Lab
then, Products
then, Black and White films
then, Tri X films
then, Tech Publication 4107
then, download the PDF file
scroll down to page 14 and you'll see the curves for TXP sheets in HC-110 & D-76
You should see the curves are pretty much the same, that you will get virtually the same look with either developer.
Go back to Black and White films, and hit T-Max films, then Pub 4016
You can also find the data for PLus X
Here is a shortcut for FP-4+. Ilford doesn't prpvide as much data, but it IS useful.
http://www.ilfordphoto.com/products/product.asp?n=6&t=Consumer+&+Professional+Films
AT Foto Import, some pretty good curves for developers are published. Here, you can get an idea of what XTOL does with many films:
http://www.fotoimport.no/pg02/PG02-1-6.htm
Finally, amazing it is STILL there, an old XTOL file, in German
http://wwwfr.kodak.com/AT/plugins/acrobat/de/professional/xtolEntwickler.pdf
scroll to page 32 and see all the charts published
My short sugestion, however, is to mix up some Xtol and soup TXP in it.
It will give more shadow speed than HC-110,
and give a mild shoulder. It will exactly, or pretty closely, give you what you want... without changing films.
d