Sony memory stick duo cards are expensive.  32GB will probably cost about $200 at time of this post.  However you can get it bit cheaper by getting an adapter and plugging in 2xmicrosd cards.  This is what the CR-5400 does.

Not much to it really.  Just plug in the microSD cards and stick it in the PSP.  I’ve had success with 2x4GB, 2x8GB and they don’t even have to be a matched set.  2GB+4GB works too.

The CR-5400 can be had at DX for about $5 so there is no excuse not to get one.  Stop paying $100 for a 16GB memory stick when you can do it for around $50 with 2x8GB microSD and an adapter.  2x16GB would also work but microSD’s of that size are still quite expensive.