All subversion clients work with different servers - the client sends its version number and basically only gets the capabilities that both system provide. Its very rare to have something that is totally incompatible.
That said, there's no reason why you shouldn't have 1.6 SVN client as well, you just need to step outside the IDE for a little. Get yourself TortoiseSVN, it'll hook itself into explorer and when things change, it'll put a little orange (or red) marker on the icon. You can work with SVN through that, using explorer. Its really nice and very easy to use.
The only thing you'll notice is if you try to use the IDE integration as well, Dreamweaver will complain that the working copy is not the right one and will not allow you to do anything with the SVN integration, so don't bother turning it on - use tortoise by itself.
The advantages of later SVN releases (better merge tracking and sparse directories, plus the few bugfixes and performance improvements) really make me recommend using Tortoise over Dreamweaver's 1.4.5 version.