Got to agree with dizzie really if you can stretch to a bit more cash and give them about 100wrms a side you'll be smiling.
I've got some Helix components (German made, parent company is Brax - very high end car audio) and they sounded ok with 75rms each, they are now getting 200 odd each and without a sub I get some nice low punchiness from them in my Audioscape pods. They even go down to the really low notes admittedly not enough cone area on them to make a big impact though.
What pods you putting them in, speakers on their own won't give you a thump unless they are installed well, a good sounding install is all mostly in the way it is installed to be honest. My car audio has been in the making a long time, and still a long way to go with my boot install but should be worth it in the end.
If you want to stay around £40 then look at these
http://www.caraudiodirect.co.uk/product_info.php?products_id=1596they seem ok for the money and i'm sure i've heard a few people on talkaudio mention about Precision Power being ok, I haven't heard any of their speakers myself though.
alternatively, have a look on
http://www.innovationaudio.co.uk, and look at Target and Diablo. My friend is the importer for the brands shown on that website and i'm sure we can look at sorting out something for you