Is it possible to install aria2 instead of transmission?

[redstone]

Being a linux noob, I am curious that if it is possible to replace the ASUS stock downloader with aria2 instead of transmission, because aria2 has more features I wanted.

 

[redstone]

I tried to use a aria2 1.1.8 which is compiled for arm machine and it would work on some ARM based NAS or ARM-board. But when I tried to start it, it won't work.
The terminal showed:

-sh: aria2: not found

However, if I use ipkg list_installed, it shows that aria2 1.1.8 is installed.Also, I can see aria2c file in /opt/bin/ .
Not sure where is wrong, guess it is not compatible with AC68U.