Better is a subjective word. If you like the Tablette 50 Signature, you may want to compare it to the D1 before selling it off. Depending on listening preference, some may prefer the Tablette 50 Signature over the D1.
There are some folks who have compared the D1 to the Response 1SC and whilst few felt they are fairly similar in sound signature, some picked the 1SC to be the superior speaker. Well, not exactly "superior", they just preferred the 1SC over the D1.
Going from the Tablette 50 Signature to the Response D1, one would likely gain a fuller and deeper bass apart from a more refined and composed sound from top to bottom, the D1 capable of revealing more detail and finer nuances present in the recording. If you prefer the forward sound and enthusiastic treble of the Tablette 50 Signature, you may find the D1 to be slightly dark at the upper frequency spectrum. Eventually it will come down to the house sound that you prefer. Having said that, the D1 (and 1SC) is considered to be a higher calibre speaker although the Tablette 50 Signature has its own appeal and different sets of strengths.