The Virginia Class submarine is already heavily armed. Each boat can carry up to 37 torpedo-sized weapons, such as Tomahawk cruise missiles. Twelve of these slots are in two vertical launch systems (VLS), known as the Virginia Payload Tubes. The new Block V (5) batch of submarines will add 28 more slots in its VLS. This is an increase of 76% of torpedo-sized weapons.
The U.S. Navy is planning to build between 72 to 78 new attack submarines. Ten of these will be the Virginia Block V boats, 8 of which will be up-armed as described here. Based on a recent briefing document from the Congressional Research Service, reported in US Naval Institute News, a total of 31 Virginia Class submarines will ultimately have this fit.
When it was originally conceived the Virginia Class was seen as a cheaper alternative to the larger Seawolf Class. The Seawolf had been designed during the Cold War to counter the latest Russian submarines. But the Russian types were mostly cancelled (or massively delayed) in the post-Cold War period. Therefore only three of the expensive Seawolfs were eventually built. Yet while the Virginia Class was smaller than the Seawolf, it took advantage of new technologies and itself became a world-leading nuclear powered attack submarine.