Your best option would be not to bother. Those old hardware EMS cards are a pain in the ass to deal with and are of very limited utility... especially on a 386-class system which natively supports both EMS and XMS using the much faster main system RAM (by way of EMM386 or similar utilities). If you want more memory in the thing, just get 4x4MB SIMMs and call it a day, focus your efforts on something else.

Why won't a soundcard work?

Well the trick with RAM cards is to find one that fits. Most of the ones I've seen are full-length cards and won't fit in the MegaPC.

I have an Intel Above Board 286 card with 2MB on it , and an AST Advantage card with 1.5MB on it. Both are detected automatically by the system BIOS as extended memory and show up on the post screen. For EMS though, they can be a pain in the arse. You gotta track down the drivers and and they can be quite finicky to work. The AST card I have is XMS only, it was not designed for EMS. The Intel card I haven't tried to configure as EMS but there are drivers on intel's website.

As for where to get them, well, same as any other retro hardware.... swap meets, dumps, forums, or worst case - ebay... the lamcsales seller tends to have a few for prices that aren't TOO outrageous.

Here's a link to a couple of EMS drivers for AST cards - REMM.SYS. Be aware with AST cards that a lot of them were made for proprietary AST computers and have an extra connector in addition to ISA (like VESA local bus but a different connector) so won't work in standard PC's.
http://dl.dropbox.com/u/9151127/oldremms.zip
http://dl.dropbox.com/u/9151127/remm470.zip

Thanks for the responses guys, I have tried some 30pin 4Mb Parity SIMMs but it just comes up with a RAM error upon posting. ATM it has 4x 30pin 1Mb Parity SIMMs installed which works fine. I know the 4Mb sticks work fine since I have tested them on another machine.
I didn't think about the RAM card sizes and yes your quite right, most of them are quite huge and will in no way fit on the Amstrad's small case.

The reason the soundcard won't work is the Ad-Lib is shared with the Megadrive side (Genesis), putting a soundcard in would mess up the system apparently.

Hmmmm, it might be worth a shot, my experience with running multiple sound cards with FM synth on them is that both cards play at once, but the system works fine.

If I come across an old Soundblaster I might give it a try. I just still don't know what i'm going to do with this RAM issue. Maybe its an unusual type of RAM I was trying out since although there are 9 chips on it (which is quite normal), they are all more-or-less matching. No chip on the far left or right is different from the rest in between.