A tarp is standalone to any tent. We have an Icarus 500 and use a Vango Family Shelter Tarp, it is huge but makes a brilliant shelter for cooking, eating and socialising under when it rains.
An Adventure tarp is smaller but very popular.
A tarp is very versatile and can be used in a variety of ways.
------------- Pitdiver
Welsue's other half and also a ,Camper, Sailor and a nearly Outdoor Person.
If you are after a shelter just to stop the rain getting in at the sloping door, then the Vango adventure tarp is big enough, but if you want a kitchen shelter, then you'll need something bigger.
Either way, as your tent has flexi-poles, I would strongly recommend that you don't wrap the tarp around the front tent pole, but keep it on king poles either side of the tent, otherwise you will start to squash the shape of the tent.
We're using a £25 Decathlon tarp with ours. It's just shy of 3m square - with some extra left-over poles, have had some interesting moments of tarp origami, as referred to by Mucker. Was looking for photos, but failed. Again.