On a Lowrance unit you'll like Navionics way better than Nauticpath. It is certainly worth the extra money. Garmin has always been known to have the best chartplotters. So the 545 (without the S) would be a great addition to your boat but it doesn't do radar and has a very small screen compared to the LCX-27/8.
If you are after a radar then the LCX series would be a good way to go. You can add the LRA-1800 or LRA-2400. Here is a link to the 1800
http://www.byownerelectronics.com/st...2&cat=0&page=1