Surprised you've mentioned Ninkas in the same sentence with the 5.3s--they're really polar opposites in terms of what they do musically and I would not consider them substitutes in any way.
If you like a deep, wide soundstage with lots of detail then go for the 5.3. If you're going with tubes in the future don't even consider the Ninkas. With Linn I find they sound best when partnered with Linn electronics, but if you're into the Linn sound you may prefer them with your electronics too. For me Linn has the pace/rhythm thing in spades but at the expense of detail, accuracy, and openness. Depends on your tastes. You might be able to get rid of your sub with the 5.3s, but the you'll probably want to keep it with the Ninkas. The 5.3s do need room to breathe to sound their best though, so if you're in a tight space they may not be a good choice.
As for B&W, a lot of people seem to like them, but they sound clinical and not particularly coherent to me. The midrange is kind of dry(especially relative to the 5.3s) and the metal tweeter can easily sound harsh with a lot of music or electronics. Seems like it's design is dominated by engineers over music lovers, but that's my taste and B&W obviously makes a great product and gets good reviews. Detail is very good as is soundstaging and imaging.
You can tell where my recommendation would lie, but it really depends on your tastes so I hope what I have outlined gives you some perspective on the different characteristics of each. As someone else mentioned, Triangle Antals would also be an excellent choice and would go head to head with the 5.3s but probably don't have quite the weight in the bass. Best of luck.
Tim
If you like a deep, wide soundstage with lots of detail then go for the 5.3. If you're going with tubes in the future don't even consider the Ninkas. With Linn I find they sound best when partnered with Linn electronics, but if you're into the Linn sound you may prefer them with your electronics too. For me Linn has the pace/rhythm thing in spades but at the expense of detail, accuracy, and openness. Depends on your tastes. You might be able to get rid of your sub with the 5.3s, but the you'll probably want to keep it with the Ninkas. The 5.3s do need room to breathe to sound their best though, so if you're in a tight space they may not be a good choice.
As for B&W, a lot of people seem to like them, but they sound clinical and not particularly coherent to me. The midrange is kind of dry(especially relative to the 5.3s) and the metal tweeter can easily sound harsh with a lot of music or electronics. Seems like it's design is dominated by engineers over music lovers, but that's my taste and B&W obviously makes a great product and gets good reviews. Detail is very good as is soundstaging and imaging.
You can tell where my recommendation would lie, but it really depends on your tastes so I hope what I have outlined gives you some perspective on the different characteristics of each. As someone else mentioned, Triangle Antals would also be an excellent choice and would go head to head with the 5.3s but probably don't have quite the weight in the bass. Best of luck.
Tim