How to use old handheld GPS

[Gruntman]

Greetings!  Long time envious lurker, recent registeree, first time poster.  I hope this is the correct place to ask.

 

This summer I've moved up from a 12' tinny to a Starcraft 18' deep V hull.  Older but in good shape and getting lots of fishing improvements; 2 electric downriggers being the biggest addition.  I hope to use them shortly on Lake Simcoe and then later (maybe next year) Lake Ontario and Erie.  My primary interest is pickerel/walleye and trout.  Salmon seems a bit out of reach now.

 

My existing electronics are likewise "small boat, casual fishing" level too:

 

Eagle Cuda 300 fish finder - pretty much the lowest cost unit I could find 7 years ago; served me well, but I think I need an upgrade.

Magellan Sportrak handle GPS (see picks below); again, very simple, purchased before GPS was everywhere.

Asus 7" tablet with Navionics US & Canada - other that screen readability issue, seems to be quite the bargain for $15 or so.

 

Since I'm not (yet) deeply invested in this, I'd like to upgrade some of this cost-effectively; when the bug digs deep I'll go for the really good stuff.

 

I'm thinking either:

 

1) Purchase a Verilux T-Box SP200 SonarPhone T-BOX to make the tablet a combo chart plotter & fish finder; very inexpensive, simple to add.  Might get a 10" tablet once I know it works well.

 

2) Purchase a suitable low-to-mid range combo device; budget: C$400.  Used/refurbed to get something up-scale but in my budget.  Eliminate the tablet, keep the ancient SportTrak handheld GPS for backup.

 

3) Purchase a combo device that lacks GPS but can use the SportTrak's NMEA data as input.  Perhaps an older, used model that was good for it's time but didn't have onboard GPS due to cost (at the time).

 

Opinions?

 

I'm specifically interested in the opinions on the table/Navionics/SonarPhone T-Box combination.  To me, with zero chartplotter knowledge, this seems like a fantastic device, especially since the tablet is essentially free (it was bought for normal tablet purposes, so I consider it already paid for) and the $15 for Navionics is virtually free, even if that's a yearly cost (am I the only one confused by their pricing?).  The $150 for the SonarPhone T-Box would be the only significant cost to me.  But, is it any good?  Is it 50% as good as a dedicated device?  20%?  90%

 

Any input appreciated!