I think you're definitely headed in the right direction with Lowrance.
You just cannot beat the expandability, versatlity, networking and ease of use. If you catch me at Bayside Marine sometime, c'mon over and I'll show you first hand what I'm talking about.
With regard to transducers, if your boat will support the installation, a thru-hull will kick most transom-mounts ass given half a chance.
Think of your transducer as the speakers of a high-end stereo system, except the 'ducer is also your "ears" as well. What you see on your fishfinder's screen is the visual representation of this underwater, ultrasonic "rock show" and if you have great speakers you have a better show!
Lowrance has also opened up the entire
Airmar Transducer catalog and if you search their site, you're in for an education!
One of the things you'll learn is the term "Multiple Element". A Multiple Element transducer has two, three or more ceramic elements whereas a typical transom mount has only one. An array of elements allow you higher performance, incredible detail and a better picture than you've ever experienced. Well worth the investment!
PS: In your previous post you asked about a cut transducer cable. Done deal dude. you cannot splice them and you can blow the display unit if the splice shorts out...Don't ask me how I learned that