Not to put to fine a point on it, espangole tastes like sh*t. As far as I know, it's only legitimate use since the beginning of the 20th Century is as a mere; it has no independent use.
Just free associating and flying on memory, but the closest finished derivative sauce to espagnole is a chasseur.
If you've got the time and can afford to waste the stock, it's probably worth going through the process all the way to, say, a butter finished bordelaise to see if you like the differences. In some ways it's a more flexible product, allowing longer holds, easier thinning if it over thickens, and so on.
Clarity is less good, than building a sauce with glace viande, but you can get as much, if not more luster, with sieving (at the appropriate points in the process), and the previously mentioned butter finish.
I do a sort of 3/4 espagnole you might want to try:
Saute 1 cup of mirepoix in 1 tsp olive oil plus 2 tbs butter, until jit shows some color. Push it to the side of the pan, and add 1 tbs of tomato paste to the center of the pan. The paste will form a fond after a minute or so. Move the mirepoix back to the center of the pan, and coat it with the paste by stirring or tossing. Keep the contents moving until the paste just begins to darken -- another 2 minutes or most. This, by the way, is called a pincage. Sprinkle 2 tbs of flour over the pincage and cook, stirring frequently, until the raw is off the flour, about 2 minutes (you can smell it). Reduce the heat to medium-low, and continue cooking the flour another five minutes, stirring frequently as the flour toasts and the tomato browns. (Now it's a roux-pincage.) Add about 1/2 cup of veal stock, raise the heat to medium-high and deglaze. Add another Add 6 cups of veal stock, bring to a boil, and reduce to a simmer. Add a bay leaf and about 10 stems worth of parsley (if you use a sachet add a little thyme too). Reduce by about one third (to 1 qt liquiid). Fine sieve through cheesecloth or a tami, pressing the essence out of the mirepoix. (And this is the quick way!)
To make a pint of demi glace, mix two cups of half-as*ed espagnole with two cup sof veal stock. Reduce slowly by one half. Add a shot of madeira, simmer an additional five minutes, and remove from heat. If you want to use the demi as a sauce on its own -- which would have Escoffier rolling over in his grave, but is perfectly legit in my book -- sieve and butter finish (in either order) before serving. Both procedures add considerable visual gloss, and the butter puts a protein sheen on the diner's lips.
Go forth and on to the derivatives,