Looking for COG-referenced wind/log instruments

[henkmeuzelaar]

I am considering to replace our 7-yr old Nexus/Comnav depth/speed/wind instruments with something else since the price of replacement sensors and display units keeps going up pretty steeply while none of the better known discount chandleries still appears to carry that line.
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Since the long axis of the Vanuatu island chain, where we have spent the past 8 seasons, parallels the predominant SE tradewind directions much of our sailing is either very close to the wind or to the jibe. Consequently, we have come to appreciate the convenience of being able to steer apparent wind angles, rather than compass headings, especially during tiring overnight stints at the wheel.
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If winds and seas are moderate and steady our Scanmar "Autohelm" windvane does most of the work. In recent years, however, the proverbially reliable tradewind belt winds and seas seem to be giving way to increasingly unpredictable wind and wave directions with confused seastates. Whether or not this primarily reflects the increasing turmoil in our aging minds , we clearly have ended up doing more hand-steering, especially at night.
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With our 5.8' wing keel draft and the stopping effects of the frequently steep waves (due to current against wind and/or overlapping wave directions) the angle between compass heading and COG can easily vary between -5 and +25 degrees. Therefore, we are looking for helm instruments able to continuously integrate wind, log and GPS information, so we can steer the correct apparent wind angles (i.e. between apparent wind direction and COG, rather than between apparent wind direction and vessel centerline) while also fine-tuning the centering of the boom when close-hauled. After all, who cares where the centerline of the boat happens to be pointing when the real direction and speed of the vessel's travel (i.e. the COG) primarily affects the apparent wind (assuming constant direction and speed of the true wind).
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I am especially eager to find out if any of the mainstream instrument lines now being offered by the discount chandleries enables full integration of wind/log/GPS data without requiring the COG data to be produced by the same brand of GPS but rather to be taken off any NMEA 0183 or 2000 input. For our remote nook of the ocean we are pretty well invested in Garmin GPSmap and Bluechart technology and the last thing I would like to bring into the mix is yet another, hard to verify, source of GPS data.
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Flying Dutchman
S/V Rivendel II (currently dry-berthed in Port Vila, Vanuatu)