3450 is equal to what Nvidia card?

6600GS?  

8400 GT iirc
Also equal (ish) in performance to a radeon 2400 and the 3200 IGP for notebooks

Probably around the performance of a 7900.

The HD 3450 gets 5.78 fps in Crysis at 1280x1024, medium graphics. That's 7 times less than the HD 3850.
http://www.legitreviews.com/article/652/7/

And now if you look at these Oblivion benchmarks, the nVidia card that gets 7 times less than the HD 3850 is 8500GT.
http://www.tomshardware.com/charts/desktop-vga-charts/oblivion-the-elder-scrolls-4-outdoor,569.html?p=1613%2C1591%2C1614%2C1601%2C1596%2C1598%2C1597%2C1602%2C1600%2C1590%2C1616%2C1612%2C1599%2C1579%2C1615%2C1594%2C1574%2C1595%2C1581%2C1643%2C1589%2C1577%2C1593%2C1637%2C1583%2C1592%2C1582%2C1635%2C1573%2C1586%2C1641%2C1570%2C1642%2C1636%2C1578%2C1640%2C1608%2C1634%2C1568%2C1572%2C1609%2C1588%2C1587%2C1580%2C1639%2C1610%2C1576%2C1611%2C1562%2C1633%2C1632%2C1638%2C1631%2C1604%2C1607%2C1560%2C1571%2C1628%2C1575%2C1630%2C1566%2C1569%2C1626%2C1624%2C1627%2C1620%2C1629%2C1585%2C1567%2C1558%2C1622%2C1625%2C1561%2C1623%2C1619%2C1606%2C1559%2C1603%2C1621%2C1565%2C1605%2C1557%2C1618%2C1564%2C1584%2C1617%2C1563

True, this is totally unscientific, because the benchmarks are for different games, but I couldn't find any other useful benchmarks for the HD 3450. It's not a gaming card, so reviewers don't often bother measuring it. It's good for HTPCs because it consumes little and supports HD and can even be fanless.

It isn't even remotely close to a 7900. The 3450 may have DX10, but the 7900 will flatten it in gaming performance.

I'd say around the 8500GT range, maybe a bit worse, but it far excels the HD performance of the 8500GT and many other cards that are much more expensive.

I built an HTCP setup for a friend recently with that card. It has exceeded my expectations. Not only is it extremely good at outputting HD content, but it's Native HDMI is extremely nice. It also consumes very little power and it runs extremely cool.