Yes, you are correct, I had forgotten he has a 1Mb Agnus. Still worth doing to have 1Mb on board and 512Kb of fast(slow) RAM.
In addition to the chips you should probably put some decoupling caps on the there - 0.33uF (I've got some if you do decide to do it, just pay for postage you can have the caps - I got a bulk lot of 50 and i've only used 2 so far.)
The extra 512K on the board is mapped into the same address space as the 512K on the trapdoor expansion. You can not use both without doing a hack that allows you to map them to different address spaces.
