I don`t see anything wrong with them being inter-mixed. Actually, I think it would be better than annuals in there, as when you pull up the annuals, you will disrupt the bulbs. Also, the perennials will hide the foliage, giving the tulips lots of time to die back naturally.

Nancy.

If you plant the tulips deeply, there's no problem planting perennials with them - you can plant them right over the bulbs and let the bulbs come up through the perennials. I do that all the time.

Darwin Hybrids are pretty reliable naturalizers because they are a cross with Fosteriana tulips, which are one of the most reliable naturalizing tulips.

One of my favorite tulip combinations that has come back for years and years and multiplies nicely is Ivory Floradale (very early - starts off a creamy yellow and fades to ivory white), Queen of the Night (a 'black' tulip) and Angelique (double pale pink that looks like a peony and grows beautifully with peonies. The peonies hide the dying foliage and the tulips look great with the emerging peony foliage - it looks like the peonies are blooming very early...)

If you want the tulips to have the best chance of returning, plant them as deep as you can and you must let the tulip foliage die completely back to the point where you can remove it with only a gentle tug on the foliage.

If you plant perennials on top and later accidentally dig the tulips up when dividing or moving the perennials, don't worry about it - just put the tulips back in the bottom of the hole, pointy end up, and plant over them again or fill the hole with soils.

This picture shows the three I mentioned:
{{gwi:202123}}

And this one shows the Ivory Floradale in its earlier yellow stage, combined with Turkestantica botanical tulips.
{{gwi:149040}}

Thank you so much. A world of gardening possibilities has just opened up for me!