I should think that the AN-LP1 would offer some improvement. While
I've not used the AN-LP1 w/the E1, I regularly use the AOR WL-500 with
the E1, and it offers a nice improvement over the whip (and an
improvement over the whip w/a Sangean ANT-60 roll-up passive antenna
connected).

Given my experience using the AN-LP1 in the past with other radios and
given the observed benefits of coupling the E1 with the active antenna
I'm currently using, I'd say it's a fairly safe bet that the AN-LP1
will offer you a noticeable improvement over the whip alone.

Junius