E-P3 Macro - close up filter?

Hi guys,

I'm a fairly experienced travel photographer, but I have only limited experience shooting macro. I'm keen to expand my shooting into this interesting field, as I'm currently living in a part of Malaysia with lots of interesting insects / flowers.

The problem is the dearth of macro lenses for M-43. I had expected the new Olympus M. Zuiko 45mm f1.8 to double as a macro lens (like the 50mm f2 macro in four-thirds format), but unfortunately it does not.

I'm thinking of buying a close-up filter as a cheap way of adapting my existing lenses. Unfortunately, M-43 lenses have an annoying array of filter sizes (Nikon standardised theirs long ago), and I would appreciate advice on which lens / filter combo to try.

My existing kit:

Olympus E-P3 camera
Olympus M. Zuiko 14-42mm (37mm thread)
Olympus M. Zuiko 40-150mm (58mm thread)

My future kit:

A short zoom, probably the Olympus M. Zuiko 9-18mm (52mm thread)

A fast prime. I'm keen on the Panasonic 20mm (46mm thread), but might wait for an x-version with faster autofocus.

I would especially appreciate advice from people who have actually used close-up filters on M-43 lenses.

Also, should I get a x2, x4, x8 or x10 filter?