well my friend hooked his amp up to the side of his trunk, which is pretty unstable cuz there's like no firm support. u could also mount ur amp underneath the passenger seat which isn't really reccomended because there's no good air flow to keep the amp cool. i'd go for a custom enclosure, if u're willing to take the time to build one or get it done. the pic of the following custom box isn't for the accord but for the prelude. this is the way i have it setup as well. the link doesn't directly send u to the pics so click on the "Audio" icon located on the upper left menu options. 5th gen prelude custom enclosure