with regard to the samson, sure you probably read this
http://forum.cakewalk.com/Guide-SONAR-usb-mic-Samson-C01u-or-C03u-mic-m1618556.aspx is it's 5th anniversary in a few weeks hehe.
but if you do a lot of work with mics a lot, then it's easier to get one that goes direct into a soundcard.. I do have a saffire 6 myself and a 1010LT on the other machine.. but... 2 negatives.. 1) m-audio aren't so great with drivers 2)although the saffire-6 has 2 mic inputs.. as instrument input, I have to use both ports to use my stereo XG unit.
so try to think where you will be in 4-6 years, as it's better to buy something you will grow into..
200-300 euro would be more than enough to get you a decent asio based card. there are only maybe 3 brands personally I'd look at currently.. RME , focusrite , roland and maybe presonus.. I wouldn't bother with a soundblaster etc.
where in europe are you based, as you may want to find a shop where you can see something in action..
pci-e is for desktops, not laptops.. so usb works externally on both machines. firewire is another option but problematic perhaps if you don't have the right chipset (Ti).. assuming you even have a firewire port :)
with regards to an amp and speakers ? they are fine for mucking about with .. but if they are home speakers, they will fluff the sound aren't truly flat.. which is what you are trying to get with studio monitors (speakers).