I've personally had a bad experience with one of the other online pet places (other than BigAls). I am all for buying excel online simply because the price can't be beat (even if almost every one of them has poor service). What we really need is someone from here to take up supplying us all with the extras we can't get from aquariumfertilizer.com. I received, on the same day, one shipment from aquariumferts and one from one of the mega pet companies above. My aquariumfert order was superb, my mega petstore order was in complete disarray. It just goes to show that the hobbiest is better suited of taking care of the other hobbiest.
I got my Excel from Bigals too. Actually I've ordered from them probably well over a dozen different times so far, always super fast shipping and never had an issue other than 4' flourescent tubes - dont even bother trying to get those.
I just started dosing excel on a regular basis. I would say that it is worth its online price (I don't think its worth it if you're paying $8.00 for 250ml). I noticed an increase in growth although it is not a "miracle pill."
If you would like just a little bit more growth I would say go for. If you're looking for a lot of growth you will probably need to upgrade a number of things.
Apart from growth... I do think it has "up-ed" the overall health of my plants.
One other thing I just thought of. If you only have a couple of plants you may want to ask some of the others on this forum if it is a good idea. If you don't have enough plants to keep the algae at bay you might just end up with a lot more algae. I am not sure about this, so you will want to get a second opinion.