abcTech.com is already taken and I'm thinking about registering abcTek.com. Sites like de.lic.io.us (I don't even know where to put the dots) still succeeded despite their horrible names (or maybe because of them?) But other sites, like google, changed their name to adhere to what people thought their name should be spelled like.
Is an alternative spelling domain name going to doom my application from the start?
'Tek' is not that much of a stretch. It can get confusing when someone tells me, "Check out, "ABC Tech dot com" and I assume the typical spelling, but more than likely, I'll get an email, read about your site and create a link. I don't know about the other company accept they were purchased by SAP. Are you in the same market and everyone is going to keep asking, "Didn't you guys get bought out by SAP?"
Be thankful a 6 letter site name is even available.
I don't think it will doom your startup and plenty of large companies started out with suboptimal domain names (GetDropBox.com, theFacebook.com, GetHarvest.com)
One thing you want to do is make sure is that you can rank first for "ABCTek " in Google because that is where people will go when they can't find ABCTech.com (~2200 results - looks good!). You also want to check to make sure that no one is dominating ABCTech in case that is what people type in. It looks decent, but there was already a company called ABCTech that was bought by SAS. Not to mention there is a video gaming company called ABCTech out of Australia.
Dharmesh Shah wrote a very detailed post on OnStartups about choosing a name for your startup:
Alternative spellings are great for helping you distinguish yourself and making you look "hip". They don't do you any good for search engine optimization though.
I think the appropriate answer to your question depends on how you plan to market your site. If people will be clicking on your links, then almost any domain name will work. If you are depending on a lot of unpaid search traffic you will have more issues. People don't search for "Tek", but they do search for "Tech". All other things considered, Tech will show up higher than Tek in a search for "tech" or "technical".
If you plan to market your site in such a way that will require people to speak your URL to other people, it needs to be easy to understand and very unambiguous. This includes TV and radio.
Good to think a unique name for your domain, but rarely our domain name also contributes to reach our site through searches, so think your domain in other's prospective what did they generally search. In this context tech is more efficacious than tek.