I fully expect the stock seat to be from somewhere between uncomfortable and excruciatingly painful. With this in mind I did a little research on what kind of aftermarket solutions are available.
The AIRHAWK
The Airhawk is the budget option, the Small model is priced around $130 on Amazon. It's cheaper than a new seat, but then again a bit pricey for what it is. (Pictured on 690 Duke) >> Airhawk
Update, June 19th
Went ahead and bought the Airhawk, more info here.
Seat Concepts
KTM factory Ergo seat
The factory ergo seat is apparenly better than stock, but inferior to other options as far as comfort goes. It's priced at $199 at KTMtwins.com so it's not a lot more than an Airhawk and it's proper seat.
>> KTMtwins.com
Touratech
SIX hundred, FIFTY NINE bucks. I could hire someone to rub my buns for that kind of money. I'll pass. Kahedo is making the seat for Touratech and you can buy seat directly from them at $479. It doesn't appear to be exactly the same but it's almost $200 cheaper.
Corbin
>> Corbin.com
Renazco
>> renazco.com
Russell seats
The Russell version looks comfortable but also rather offensive on the Enduro. The pricing on the website is so complicated that I could not be bothered especially when the look of the seat is not what I'm willing to live with.
>> day-long.com
Other options
XPC Racing
>> http://www.xpcracing.com/
Not really sure if they offer a seat for the 690. Bad website.
BMS
>> http://billmayer-saddles.com/
I would need to send in the stock seat. Not an option. Another not so great website.
CONCLUSION
The Seat Concepts seat looks like the way to go. Pricing is reasonable and the shape looks to be a good compromise.
EDIT 5.5. 2014
I went against my better judgement and got the Powerparts seat. Mostly because that was the only seat that did not require an overseas purchase. More about the KTM ERgo seat in here.