If it was me, I would NOT go with an HDS 5. I use all lowrance products and have an HDS 5. In my opinion, they are just too hard to see. They do one thing at a time very well. Yes, you can run split screen and even tri-screen however, anything more than one view on the screen is hard to read.

I put an HDS 5 in my dads boat. I have a 7 and a 10 and on another boat a 7 and an 8. The 5 was frustrating to even look at. I ended up swapping an HDS 7 with him.

The 7 will run split screen very well. Tri-screen is harder to see. The 8 runs tri-screen very well but quad screen is lacking. The 10 runs all four just fine.
The LSS-2 is way better than the one is (have them both) and it gives you the ability to network and add network components as you go. I have a bow mounted trolling motor with a universal sonar mounted in it. It is hooked to my HDS 7. The 7 is networked to the LSS 2. I have an HDS 10 at the helm connected to the rear transducer. The 10 is also hooked to the LSS 2. I can view either transducer from either unit. Make sure you bundle all the yellow wires together from the power packs on each unit. This way you can "wake" the LSS 2 without having it powered on all the time (there is no on and off switch).

That said, The lowrance does a ton of stuff really well. Side by side with a Bird however, the bird just seems to have better downscan features. I've never used their side scan, but the downscan is way more crisp and clear than the lowrance. Plus, the birds interact with the popular Minn-kota motors whereas the Lowrance works with the MotorGuide.

Just some ideas and stuff to think about.